Electrode for plasma display panel and process for producing the same

ABSTRACT

An electrode, for a plasma display panel, adapted for provision on a front or back plate of a plasma display panel, the electrode comprising a conductive paste.

This is a Division of application Ser. No. 08/787,744 filed Jan. 24,1997.

BACKGROUND OF THE INVENTION

The present invention relates to a plasma display panel (hereinafteroften referred to as “PDP”) which is a plate display of aself-activation luminescence type using gas discharge, and moreparticularly to an electrode to be provided on a front or back plate ofPDP.

In general, PDP comprises: two opposed glass substrates; a pair ofelectrodes systematically arranged in the glass substrates; and a gas(mainly Ne or the like) sealed therebetween. A voltage is applied acrossthe electrodes to produce discharge within minute cells around theelectrodes to emit light from each cell, thereby displaying information.Systematically arranged cells are selectively subjected to dischargeluminescence in order to display information. Such PDPs are classifiedinto two types, a direct current type PDP, wherein electrodes areexposed to a discharge space (DC type), and an alternating current type(AC type) wherein electrodes are covered with an insulating layer. Eachof these types is further classified into a refresh drive system and amemory drive system according to display functions and drive systems.

FIG. 1 shows an embodiment of the construction of an AC type PDP. In thedrawing, the front plate and the back plate are shown separately fromeach other. As shown in the drawing, two glass substrates 1, 2 arearranged parallel and opposite to each other. Both the substrates aredisposed so as to be held, while leaving a given space therebetween, bymeans of cell barriers 3 provided, parallel to each other, on the glasssubstrate 2 as a back plate. Composite electrodes 6 each comprising asustaining electrode 4 as a transparent electrode and a bus electrode 5as a metallic electrode are provided parallel to each other on the backside of the glass substrate 1 as the front plate, and a dielectric layer7 is provided so as to cover the composite electrode. Further, aprotective layer 8 (MgO layer) is provided on the surface of thedielectric layer 7. On the other hand, address electrodes 9 are providedbetween the cell barriers 3 on the front side of the glass substrate 2as the back plate so that the address electrodes 9 are parallel to eachother and orthogonal to the composite electrodes 6. Further, a phosphor10 is provided so as to cover the wall surface of the cell barriers 3and the bottom face of cells. The AC type PDP is of a plane dischargetype and constructed so that an alternating voltage is applied acrossthe composite electrodes on the front plate and an electric field leakedin the space produces discharge. In this case, since the alternatingvoltage is applied, the direction of the electric field changesaccording to the frequency. Ultraviolet light produced by the dischargepermits the phosphor 10 to emit light, and light transmitted through thefront plate is viewed by an observer.

Regarding the composite electrode 6 on the front plate of the AC -typePDP, it should be noted that sole use of the sustaining electrode 4results in high resistance value, and, hence, the bus electrode 5 isformed on the sustaining electrode 4 in order to lower the resistancevalue. ITO, SnO₂, ZnO and the like are considered as a material for thesustaining electrode 4. In general, however, ITO is used from theviewpoints of easy film formation and patterning. On the other hand, thebus electrode is formed of a metallic material. When it is constitutedby a single layer of a thin metallic film, use of a material having lowresistivity, for example, Cu or Al, is considered from the viewpoint ofresistance value required of the bus electrode 5. Cu, when used for thebus electrode, has poor adhesion to ITO as a layer underlying the buselectrode 5 and, in addition, as a result of firing in the formation ofa dielectric layer 7 in the subsequent step, is thermally oxidizedresulting in increased resistance value. On the other hand, use of Alposes a problem that the firing in the subsequent step results inthermal oxidation of the material or the roughening of the surface.Therefore, it is common practice to construct the bus electrode 5 out ofa combination of dissimilar metallic materials, such as Cr/Cu/Cr orCr/Al/Cr, rather than a single layer of a metallic thin film. In thiscase, Cr constituting a lower layer functions as a layer for adhesion tothe underlying sustaining electrode 4, and Cr constituting an upperlayer functions as a layer for antioxidation of overlying Cu or Al. Theuse of the above laminate structure and materials is not limited to theelectrode of the above AC type PDP but applicable also to the electrodeof the DC type PDP for the same reason described above in connectionwith the electrode of the AC type PDP. The adoption of the abovelaminate structure does not pose a problem associated with the singlemetallic layer. It, however, requires a thin film forming technique,such as sputtering or vapor deposition, and etching three times in theformation of the bus electrode, rendering the process complicated, whichin turn takes a lot of time and results in unsatisfactory throughputcapacity.

In view of the above, the present invention has been made, and an objectof the present invention is to provide a PDP electrode which can beprepared by a simple process, and a process for producing the same.

Another object of the present invention is to provide means for formingan electrode which can realize a high display quality even in ahigh-definition or large-area plasma display panel.

DISCLOSURE OF THE INVENTION

Under the above circumstances, the present invention has been made, andbasically, the present invention provides an electrode, for a plasmadisplay panel, adapted for provision on a front or back plate of aplasma display panel, the electrode comprising a conductive paste. Inparticular, the electrode of the present invention is characterized bycomprising a black pigment.

Further, the present invention provides a particular thick filmproduction process as an excellent process for producing the aboveelectrode layer.

Furthermore, in order to improve the above electrode, the presentinvention provides an electrode having therein a particular two layerstructure and an electrode production process involving transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing one embodiment of theconstruction of an AC type plasma display panel;

FIGS. 2A to 2D are a process diagram showing a first embodiment forforming a composite electrode on a front plate;

FIGS. 3A to 3F are a process diagram showing a second embodiment forforming a composite electrode on a front plate;

FIGS. 4A to 4E are a process diagram showing a third embodiment forforming a composite electrode on a front plate;

FIGS. 5A to 5E are a process diagram showing a fourth embodiment forforming a composite electrode on a front plate;

FIGS. 6A to 6E are a process diagram showing a fifth embodiment forforming a composite electrode on a front plate;

FIGS. 7A to 7E are a process diagram showing one embodiment of theprocess for producing a thick film pattern according to the presentinvention;

FIGS. 8A to 8C are a process diagram showing one embodiment of theprocess for producing an electrode of a plasma display panel accordingto the present invention;

FIGS. 9A to 9C are a process diagram showing another embodiment of theprocess for producing a plasma display panel according to the presentinvention;

FIGS. 10A to 10D are a process diagram showing a further embodiment ofthe process for producing a plasma display panel according to thepresent invention;

FIGS. 11 to 13 are schematic cross-sectional views showing an embodimentof the transfer sheet for an electrode of a plasma display panelaccording to the present invention;

FIGS. 14A to 14C,

FIGS. 15A and 15B,

FIGS. 16A to 16C,

FIGS. 17A to 17C,

FIGS. 18A to 18D,

FIGS. 19A to 19C,

FIGS. 20A to 20C,

FIGS. 21A to 21C,

FIGS. 22A to 22E

FIGS. 23A to 23E,

FIGS. 24A to 24E, and

FIGS. 25A to 25F are process diagrams respectively showing embodimentsof the process for producing an electrode of a plasma display panelaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[A] Composite Electrode for PDP

The electrode for a plasma display panel according to the presentinvention is an electrode, for a plasma display panel, adapted forprovision on a front or back plate of a plasma display panel, theelectrode comprising a conductive paste.

According to the present invention, the above conductive paste may be inthe form of a sheet prepared by coating a conductive paste and dryingthe coating.

Further, according to the present invention, a black pigment may beincorporated into the conductive paste so that the conductive pasteserves also as a black matrix.

A transparent electrode of a transparent conductive film may be providedbetween the electrode and a substrate to form a composite electrodestructure.

The electrode may be prepared by any of screen printing using aconductive paste, etching of a conductive material, filling of aconductive paste, and photolithography using a photosensitive conductivematerial.

A composition comprising, on a solid basis (i.e., excluding a solvent),98 to 60% by weight (90 to 60% by weight in the case of a photosensitivematerial), preferably 90 to 75% by weight, of a metallic powder, 2 to40% by weight (10 to 40% in the case of a photosensitive material),preferably 10 to 25% by weight of an organic solid matter may be used asthe conductive paste. Preferably, the metallic powder as the conductivecomponent is selected from the group consisting of powders of Ag, Au,Ni, Cu, Ag—Pd, and Al.

Preferred binders usable herein include a polymer of one member or acopolymer of at least two members selected from methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate,n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate,sec-butyl acrylate, sec-butyl methacrylate, isobutyl acrylate, isobutylmethacrylate, tert-butyl acrylate, tert-butyl methacrylate, hydroxyethylacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,hydroxypropyl methacrylate and the like; ethyl cellulose, a polybutenederivative; and styrene and a-methylstyrene.

In the present invention, the conductive paste may further comprise ablack pigment. The incorporation of the black pigment permits theconductive paste to function also as a black matrix. Further, use may bemade of a laminate structure of a black conductive layer containing ablack pigment and a conductive layer not containing a black pigment.

In the case of a composite electrode of a laminate of the aboveelectrode and a transparent electrode, the first layer of a transparentconductive film for the transparent electrode may be made of ITO, SnO₂,ZnO or the like. Among them, ITO and SnO₂ are preferred as the materialfor the transparent electrode.

The transparent conductive film may be formed, for example, by forming atransparent conductive film on a glass substrate as the substrate andpatterning the transparent conductive film by photolithography to createa predetermined pattern.

In the above composite electrode, the second layer may be formed byscreening using a conductive paste, etching, or filling using aconductive paste. Specific embodiments of these methods will bedescribed in detail in working examples described below. The formationof the second layer by photolithography using a photosensitive paste isalso possible. In this case, a method, described below, is particularlypreferred which comprises the steps of: once forming a photosensitivepaste into a film; laminating the film onto a substrate; and patterningthe film by photolithography.

The composition and properties of the conductive paste will be describedlater. They are described in more detail also in the followingdescription in connection with the composite electrodes having a twolayer structure. These compositions and production processes areapplicable to the present invention.

[B] Process for Producing Electrode Pattern

Processes which are considered usable for the production of an electrodeof PDP include one wherein a film of an electrode material is formed ona substrate by the above-described vacuum deposition, sputtering,plating, thick film formation or the like and the film is patterned byphotolithography and one wherein patterning is performed by screenprinting using a thick paste film. The former method, i.e., the methodusing photolithography, has an advantage of high pattern accuracy. It,however, is disadvantageous in that the formation of a film by vacuumdeposition or sputtering has poor mass productivity, resulting inincreased cost. The formation of a film by plating disadvantageouslyinvolves many steps.

Accordingly, an object of the present invention is to provide a processfor producing an electrode pattern which enables a pattern to be formedwith a high accuracy by simple steps.

In order to attain the above object, the process for producing anelectrode pattern as a first type of pattern according to the presentinvention comprises at least the following steps:

(1) the first step of forming previously coating a photosensitive pasteon a film to form a pattern forming layer on the film;

(2) the second step of laminating the film onto a substrate so that thepattern forming layer faces the substrate;

(3) the third step of exposing the pattern forming layer from above thefilm through a predetermined mask;

(4) the fourth step of separating and removing the film and developingthe pattern forming layer to remove unexposed areas; and

(5) the fifth step of firing the whole substrate to adhere the patternforming layer in its exposed areas to the substrate.

Further, in order to attain the same object, the process for producing athick film pattern as a second type of pattern comprises at least thefollowing steps:

(1) the first step of forming previously coating a photosensitive pasteon a film to form a pattern forming layer on the film;

(2) the second step of laminating the film onto a substrate so that thepattern forming layer faces the substrate;

(3) the third step of separating and removing the film and exposing thepattern forming layer through a predetermined mask;

(4) the fourth step of developing the pattern forming layer to removeunexposed areas; and

(5) the fifth step of firing the whole substrate to adhere the patternforming layer in its exposed areas to the substrate.

According to the present invention, when the substrate is a glasssubstrate, an address electrode for PDP may be formed. On the otherhand, when the substrate has thereon a patterned transparent conductivefilm, a composite electrode (a bus electrode) for PDP may be formed.

FIG. 7 is a process diagram showing an embodiment of the process forproducing an electrode pattern according to the present invention.

As shown in FIG. 7A, a photosensitive paste is coated on a film 711 as aflexible substrate, and the coating is dried to form a pattern forminglayer 712. Films usable as the film 711 include polyethyleneterephthalate (PET), adhesive PET, silicone-treated PET,acrylmelamine-treated PET, wax-treated PET, stretched polyethylene,polyethylene, stretched polypropylene, polypropylene, triacetylcellulose, polystyrene, polyethylene naphthalate, polyimide and otherfilms. The thickness of the film 711 is suitably 6 to 200 μm. When thethickness is less than 6 μm, the nerve is low resulting in poorworkability and remarkable curling. On the other hand, when it is morethan 200 μm, the film is heavy, making it difficult to roll. Thephotosensitive paste may be coated on the film 711 by any suitable meanssuch as roll coating, die coating, slip coating, doctor blade coating,Komma coating, or gravure coating.

When the thick film pattern is intended to be used as an electrode, aconductive paste comprising a photosensitive resin component and aconductive powder (such as Au, Ag, Cu, Ni, or Al) and optionally a glassfrit and an inorganic pigment is used as the photosensitive paste.

The proportion of the inorganic component (glass frit, metallic powder,inorganic pigment or the like) to the photosensitive resin component(negative-working type) in the photosensitive paste is such that theamount of the photosensitive resin component is 10 to 100 parts byweight, preferably 10 to 50 parts by weight, based on 100 parts byweight of the inorganic component. When the amount of the photosensitiveresin component is smaller than 10 parts by weight, it is impossible toperform patterning, while when it is larger than 100 parts by weight,sintering does not provide any dense structure, making it impossible tooffer contemplated properties. Preferably, the glass frit used has asoftening point of 400 to 650° C. and an average particle diameter of0.1 to 10 μm. A mixture of two or more glass frits may also be used.

The photosensitive resin component comprises an alkali-developablebinder polymer and a reactive monomer and, if necessary, may furthercomprise an initiator, a sensitizer, a polymerization terminator, achain transfer agent, a defoamer, a leveling agent, a dispersant, aplasticizer, a stabilizer and the like.

Alkali-developable binder polymers usable herein include, but are notlimited to, a copolymer of at least one member, selected from acrylicacid, methacrylic acid, a dimer of acrylic acid (M-5600, manufactured byToa Gosei Chemical Industry Co., Ltd.), itaconic acid, crotonic acid,maleic acid, fumaric acid, vinylacetic acid, and acid anhydrides of theabove compounds, with at least one member selected from methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propylacrylate, n-propyl methacrylate, isopropyl acrylate, sec-butyl acrylate,sec-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate,tert-butyl acrylate, tert-butyl methacrylate, n-pentyl acrylate,n-pentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate,n-octyl methacrylate, n-decyl acrylate, n-decyl methacrylate, styrene,α-methylstyrene, and N-vinyl-2-pyrrolidone, the copolymer having an acidvalue of 50 to 200 mg KOH/g. The copolymers may be used alone or as amixture of two or more. Polymers comprising an ethylenically unsaturatedcompound having a glycidyl or hydroxyl group added to the abovecopolymers, the polymers having an acid value of 50 to 200 mg KOH/g, mayalso be used. They may be used alone or as a mixture of two or more. Atleast one non-alkali-developable polymer may be blended with the abovepolymers. Non-alkali-developable polymers usable herein includepolyvinyl alcohol, polyvinyl butyral, acrylic ester polymer, methacrylicester polymer, polystyrene, α-methylstyrene polymer,1-vinyl-2-pyrrolidone polymer, and copolymers thereof.

The reactive monomer may be a compound having at least one polymerizablecarbon-carbon unsaturated bond, and specific examples thereof includeallyl (meth)acrylate, benzyl (meth)acrylate, butoxyethyl (meth)acrylate,butoxyethylene glycol (meth)acrylate, cyclohexyl (meth)acrylate,dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate,2-ethylhexyl (meth)acrylate, glycerol (meth)acrylate, glycidyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, isobornyl (meth)acrylate, isodexyl (meth)acrylate,isooctyl (meth)acrylate, lauryl (meth)acrylate, 2-methoxyethyl(meth)acrylate, methoxyethylene glycol (meth)acrylate, phenoxyethyl(meth)acrylate, stearyl (meth)acrylate, ethylene glycoldi(meth)acrylate, diethylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,4-cyclohexanedioldi(meth)acrylate, 2,2-dimethylolpropane di(meth)acrylate, glyceroldi(meth)acrylate, tripropylene glycol di(meth)acrylate, glyceroltri(meth)acrylate, trimethylolpropane tri(meth)acrylate,polyoxyethylated trimethylolpropane tri(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate, triethyleneglycol di(meth)acrylate, polyoxypropyl trimethylolpropanetri(meth)acrylate, butylene glycol di(meth)acrylate, 1,2,4-butanetrioltri(meth)acrylate, 2,2,4-trimethyl-1,3-pentanediol di(meth)acrylate,diallyl fumarate, 1,10-decanediol dimethyl (meth)acrylate,dipentaerythritol hexa(meth)acrylate,γ-methacryloxypropyltrimethoxysilane, and 1-vinyl-2-pyrrolidone. In thepresent invention, these monomers may be used alone or a mixture of twoor more of them, or alternatively may be used in the form of othercompounds.

Photopolymerization initiators to be added for constituting thephotosensitive resin component include benzophenone, methylo-benzoylbenzoate, 4,4-bis(dimethylamine)benzophenone,4,4-bis(diethylamine)benzophenone, α-amino-acetophenone,4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzylketone, fluorenone, 2,2-diethoxyacetophenone,2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone,p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone,2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone,benzyl dimethyl ketal, benzyl methoxyethyl acetal, benzoin methyl ether,benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone,2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone,dibenzsuberone, methyleneanthrone, 4-azidobenzylacetophenone,2,6-bis(p-azidobenzylidene)cyclohexane,2,6-bis(p-azidobenzylidene)-4-methylcyclohexanone,2-phenyl-1,2-butanedion-2-(o-methoxycarbonyl)oxime,1-phenyl-propanedion-2-(o-ethoxycarbonyl)oxime,1,3-diphenyl-propanetrion-2-(o-ethoxycarbonyl)oxime,1-phenyl-3-ethoxy-propanetrion-2-(o-benzoyl)oxime, Michler's ketone,2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, naphthalenesulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone,4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide,triphenylphosphine, camphorquinone, carbon tetrabromide,tribromophenylsulfone, benzoin peroxide, and a combination of aphotoreducible dye, such as eosine or Methylene Blue, with a reducingagent, such as ascorbic acid or triethanolamine. In the presentinvention, these photopolymerization initiators may be used alone or asa mixture of two or more.

When the volatile or decomposition temperature exceeds 600° C., hightemperature is required for removing the resin component after exposureand development of the photosensitive black conductive paste coating andthe photosensitive conductive paste coating, which, for example, whenthe heat resistance of the insulating plate is low, thermal deformationis unfavorably created in the substrate. On the other hand, there is noparticular limitation on the volatilization or decompositiontemperature. However, the lower the volatilization or decompositiontemperature, the smaller the number of kinds of completely volatilizableor decomposable resins and, hence, the narrower the range of selectablematerials. For this reason, the lower limit of the volatilization ordecomposition temperature of the photosensitive resin component ispreferably, for example, about 200° C.

The content of the photosensitive resin component in the photosensitiveconductive paste is preferably 5 to 40% by weight.

The photosensitive conductive paste used in the present invention mayfurther comprise optional additives, such as a sensitizer, apolymerization terminator, a chain transfer agent, a leveling agent, adispersant, plasticizer, a stabilizer, and a defoamer.

Solvents usable herein include methanol, ethanol, isopropanol, acetone,methyl ethyl ketone, toluene, xylene, cyclohexanone, methylene chloride,3-methoxybutyl acetate, ethylene glycol monoalkyl ethers, ethyleneglycol dialkyl ethers, diethylene glycol monoalkyl ethers, diethyleneglycol monoalkyl ether acetates, propylene glycol monoalkyl ethers,propylene glycol dialkyl ethers, propylene glycol monoalkyl acetates,dipropylene glycol monoalkyl ethers, dipropylene glycol dialkyl ethers,dipropylene glycol monoalkyl ether acetates, and terpenes such as α- orβ-terpineol. They may be used alone or as a mixture of two or more.

As shown in FIG. 7B, the film 711 having thereon the pattern forminglayer 712 is laminated onto a glass substrate 713 so that the patternforming layer 712 faces the glass substrate 713. Thereafter, as shown inFIG. 7C, the pattern forming layer 712 is exposed from above the film711 through a predetermined mask M. In this case, an ionizing radiation,such as electron beam, ultraviolet radiation, or X-radiation, is used asa light source. The exposure of the pattern forming layer 712 causes thepattern forming layer 712 to be separated into an unexposed area 712 aand an exposed area 712 b. As shown in the drawing, when the exposure isperformed with the mask M in intimate contact with the film 711 withoutremoving the film 711, the fusion effect of oxygen offers an improvementin sensitivity (shortening of exposure time) and other effects. Further,when the photosensitive paste material has an adhesive property,exposure with the mask adhered to the film 711 without removing the film711 is effective.

Subsequently, the film is separated and removed, and, as shown in FIG.7D, the pattern forming layer 712 is developed to remove the unexposedarea 712 a. When an increase in film thickness is contemplated, it isalso possible to use a method wherein a series of steps of laminatingthe film with a pattern forming layer provided thereon, exposing thepattern forming layer, and separating and removing the film are repeatedfollowed by development at a time. Finally, the whole substrate is firedto adhere the pattern forming layer in its exposed area 712 b to theglass substrate as shown in FIG. 7E, thereby creating a predeterminedthickened film pattern 714.

When the pattern forming layer 712 is non-tacky due to the nature of thematerial for the photosensitive paste, the film 711 may be separated andremoved followed by exposure. In this case, it is also possible to use amethod wherein a series of steps of laminating the film with a patternforming layer provided thereon, separating and removing the film, andexposing the pattern forming layer are repeated followed by developmentat a time. Further, the laminate shown in FIG. 7A may be stored with aprotective film provided on the pattern forming layer 712, and, beforethe step shown in FIG. 7B, the protective film may be removed andlaminated onto the glass substrate 713. The protective film is providedin order to prevent damage to the surface, inclusion of contaminants,blocking and other unfavorable phenomena. Preferably, the protectivelayer has a thickness of preferably 1 to 400 μm, more preferably 4.5 to200 μm, and is constituted, for example, by a polyethylene terephthalatefilm, a 1,4-polycyclohexylene dimethylene terephthalate film, apolyethylene naphthalate film, a polyphenylene sulfide film, apolystyrene film, a polypropylene film, a polysulfone film, an aramidfilm, a polycarbonate film, a polyvinyl alcohol film, a film of acellulose derivative, such as cellophane or cellulose acetate, apolyethylene film, a polyvinyl chloride film, a nylon film, a polyimidefilm, an ionomer film or the like, the protective film in its side to belaminated onto the pattern forming layer having been treated withsilicone, acrylmelamine, wax or the like for rendering the protectivefilm releasable.

[C] Composite Electrode Having Two Layer Structure

The conventional electrode (display electrode) provided on the frontplate of PDP is a transparent electrode made of indium tin oxide (ITO).This transparent electrode has higher electric resistance than anelectrode made of a metallic conductive material and, in particular,when used in a high-definition plasma display panel or a large-areaplasma display panel, exhibits remarkably increased electric resistance,deteriorating the display quality or requiring the application of highvoltage.

In order to solve this problem, the formation of a silver paste layer onthe transparent electrode is considered effective for reducing theresistance of the display electrode. This method, however, isdisadvantageous in that the display contrast is lowered because thesilver paste is whitish. For this reason, a black conductive layershould be provided on the transparent electrode to reduce the resistanceof the display electrode, and, in addition, the contrast and colorpurity in the case of viewing of the display panel from the front plateside should be enhanced. At the present time, however, no blackconductive layer having a blackness high enough to maintain a highdisplay quality and, at the same time, low electric resistance hashitherto been proposed in the art, posing a problem that either theadverse effect on the display quality or the increase in electricresistance is unavoidable.

Under the above circumstances, the present invention aims to provide aprocess for producing an electrode which can offer high display qualityeven in a high-definition or large-area plasma display panel.

The process for producing an electrode of a plasma display panelaccording to the first invention comprises the steps of: coating aphotosensitive black conductive paste containing a black pigment on aninsulating substrate and drying the coating to form a photosensitiveblack conductive paste coating; coating a photosensitive conductivepaste on the photosensitive black conductive paste coating and dryingthe coating to form a photosensitive conductive paste coating; exposingthe photosensitive black conductive paste coating and the photosensitiveconductive paste coating through a mask having a predetermined pattern;developing the exposed coatings; and then firing the developed coatingsto form an electrode having a two layer structure of a black conductivelayer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the second invention comprises the steps of: coating aphotosensitive black conductive paste containing a black pigment on aninsulating substrate and drying the coating to form a photosensitiveblack conductive paste coating; exposing the photosensitive blackconductive paste coating through a mask having a predetermined pattern;coating a photosensitive conductive paste on the photosensitive blackconductive paste coating and drying the photosensitive conductive pastecoating; performing exposure through a mask having a predeterminedpattern; and developing and firing the photosensitive black conductivepaste coating and the photosensitive conductive paste coating to form anelectrode having a two layer structure of a black conductive layer and amain conductive layer.

The process for producing an electrode of a plasma display panelaccording to the third invention comprises the steps of: coating aphotosensitive black conductive paste containing a black pigment on aninsulating substrate and drying the coating to form a photosensitiveblack conductive paste coating; exposing the photosensitive blackconductive paste coating through a mask having a predetermined patternand developing the exposed photosensitive black conductive paste coatingto form a black conductive layer; coating a photosensitive conductivepaste so as to cover the black conductive layer and drying the resultantphotosensitive conductive paste coating; and exposing the photosensitiveconductive paste coating through a mask having a predetermined patternand developing the exposed photosensitive conductive paste coating toform a main conductive layer on the black conductive layer, therebypreparing an electrode having a two layer structure.

According to the above present invention, in the electrode having a twolayer structure of a black conductive layer and a main conductive layereach formed of a photosensitive paste, the main conductive layerfunctions to lower the electric resistance of the transparent electrode,while the black conductive layer functions to improve the connection ofthe main conductive layer to the transparent electrode and, at the sametime, to enhance the contrast and color purity of the display panel.

According to the present invention, when the substrate is a glasssubstrate, an address electrode for PDP may be formed. On the otherhand, when the substrate has thereon a patterned transparent conductivefilm, a composite electrode (a bus electrode) for PDP may be formed.

The best mode for carrying out the invention will be described. Theformation of a bus electrode on a transparent electrode of a front panelin an AC type PDP will be described by way of example.

FIG. 8 is process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the firstinvention. In FIG. 8, a photosensitive black conductive paste containinga black pigment is coated so as to cover a transparent electrode 82provided on an insulating substrate 81, and the coating is dried to aphotosensitive black conductive paste coating 83 (FIG. 8A). Thephotosensitive black conductive paste coating 83 may be formed by screenprinting, blade coating, roll coating, die coating, film transfer (whichwill be described later) or other method(s), and the thickness of thephotosensitive black conductive paste coating 83 is preferably about 1to 15 μm. The transparent electrode 82 may be made of a conventionaltransparent conductive material, such as indium tin oxide (ITO) or tinoxide (SnO₂).

A photosensitive conductive paste is then coated on the photosensitiveblack conductive paste coating 83, the coating is dried to form aphotosensitive conductive paste coating 84, and the photosensitive blackconductive paste coating 83 and the photosensitive conductive pastecoating 84 are exposed at a time through a mask 810 having apredetermined pattern (FIG. 8B). The photosensitive conductive pastecoating 84 may be formed by screen printing, blade coating, rollcoating, die coating, film transfer or other method(s), and thethickness of the photosensitive conductive paste coating 84 ispreferably about 1 to 20 μm. In this exposure, light, which has beenpassed through the mask 810 and applied to the photosensitive conductivepaste coating 84, exposes the photosensitive conductive paste coating 84and, at the same time, is transmitted through the photosensitiveconductive paste coating 84 and exposes the photosensitive blackconductive paste coating 83. The above exposure may be performed using alight source, such as a high-pressure mercury lamp, a low-pressuremercury lamp, a medium-pressure mercury lamp, an ultrahigh-pressuremercury lamp, a xenon lamp, a mercury short arc lamp, a metal halidelamp, an X-radiation, or an electron beam.

Subsequently, the photosensitive black conductive paste coating 83 andthe photosensitive conductive paste coating 84 are developed at a timeand then fired to remove the resin component of the photosensitive pasteto form an electrode 85 having a two layer structure of a blackconductive layer 86 and a main conductive layer 87 on the transparentelectrode 82 (FIG. 8C).

The photosensitive black conductive paste used in the formation of anelectrode for a plasma display panel comprises a photosensitiveconductive paste and a black pigment incorporated thereinto. Blackpigments usable herein include conductive black pigments, such as carbonblack and titanium black, Co—Cr—Fe, Co—Mn—Fe, Co—Fe—Mn—Al, Co—Ni—Cr—Fe,Co—Ni—Mn—Cr—Fe, Co—Ni—Al—Cr—Fe, and Co—Mn—AlCr—Fe—Si. The black pigmenthas an average particle diameter of about 0.01 to 5 μm and may beincorporated in amount of 0.1 to 50 parts by weight based on 100 partsweight of the conductive powder contained in the photosensitiveconductive paste. When the average particle diameter of the blackpigment is less than 0.01 μm, the production of such fine particles isdifficult and, in addition, the thixotropy of the photosensitive blackconductive paste is unfavorably large. On the other hand, when theaverage particle diameter exceeds 5 μm, uneven color is likely to occur.When the content of the black pigment is less than 0.1 part by weight,the coloring is unsatisfactory. On the other hand, a black pigmentcontent exceeding 50 parts by weight unfavorably results in increasedresistance and, at the same time, remarkably lowered light transmissionto cause unsatisfactory curing in exposed areas of the photosensitiveblack conductive paste coating 83.

The photosensitive conductive paste used in the formation of thephotosensitive black conductive paste and the photosensitive conductivepaste used in the formation of the photosensitive conductive pastecoating 84 comprise at least a conductive powder and a photosensitiveresin component and, if necessary, an inorganic powder for improving theadhesion to the substrate or other purposes.

The conductive powder may be at least one member selected from Au, Ag,Cu, Ni, Al, Ag—Pd and other powders. The form of particles constitutingthe conductive powder may be any one such as a spherical, flaky, mass,conical, or rod form. Among them, a spherical conductive powder ispreferred from the viewpoints of freedom from agglomeration and havinggood dispersibility, and the average particle diameter is preferably0.05 to 10 μm. When the average particle diameter of the conductivepowder is less than 0.05 μm, the structural viscosity (thixotropy) ofthe photosensitive conductive paste is unfavorably large. On the otherhand, when the average particle diameter of the conductive powderexceeds 10 μm, the permeability of the photosensitive conductive pastecoating 84 to light is unsatisfactory, adversely affecting the exposureof the photosensitive black conductive paste coating 83. Preferably, theconductive powder has a specific surface area of 0.1 to 3 m²/g from theviewpoint of pattern edge accuracy. The above conductive powder may beincorporated in an amount of 45 to 93% by weight into the photosensitiveconductive paste.

Inorganic powders which may be optionally added to the photosensitiveconductive paste include, for example, a glass frit having a softeningtemperature of 400 to 650° C. and a coefficient of thermal expansionα₃₀₀ of 60×10⁻⁷ to 100×10⁻⁷/° C. When the softening temperature of theglass frit exceeds 650° C., the firing temperature should be increased.In this case, for example, when the heat resistance of the insultingsubstrate is low, thermal deformation is unfavorably created in theinsulating substrate at the stage of firing. On the other hand, when thesoftening temperature of the glass frit is below 400° C., the glass fritis fused before complete decomposition and volatilization of the resincomponent in the photosensitive black conductive paste and thephotosensitive conductive paste, unfavorably creating voids. When thecoefficient of thermal expansion a₃₀₀ is less than 60×10⁻⁷/° C. orexceeds 100×10⁻⁷/° C., the difference in coefficient of thermalexpansion between the glass frit and the glass substrate is excessivelylarge, creating deformation or the like. The average particle diameterof the glass frit is preferably 0.1 to 5 μm.

The photosensitive resin component constituting the photosensitiveconductive paste comprises at least an alkali-developable binder polymerand a monomer and, if necessary, an initiator and a solvent. Uponfiring, it is volatilized and decomposed and does not leave any carbidein the pattern. Materials described in the above item [B] may be usedfor the photosensitive resin component.

FIG. 9 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the secondinvention. In FIG. 9, a photosensitive black conductive paste containinga black pigment is coated so as to cover a transparent electrode 82provided on an insulating substrate 81, and the coating is dried to forma photosensitive black conductive paste coating 83, the photosensitiveblack conductive paste coating 83 is exposed through a mask 811 having apredetermined pattern (FIG. 9A). The photosensitive black conductivepaste, the process for producing the photosensitive black conductivepaste coating 83, and the thickness of the photosensitive blackconductive paste coating 83 used herein are the same as those in theprocess for producing an electrode according to the first invention.Light sources usable herein are the same as those described above inconnection with the process for producing an electrode according to thefirst invention.

A photosensitive conductive paste is then coated on the exposedphotosensitive black conductive paste coating 83, and the coating isthen dried to form a photosensitive conductive paste coating 84, and thephotosensitive conductive paste coating 84 is exposed through a mask 812having a predetermined pattern (FIG. 9B). The photosensitive conductivepaste, the process for producing the photosensitive conductive pastecoating 84, and the thickness of the photosensitive conductive pastecoating 84 used herein are the same as those in the process forproducing an electrode according to the first invention. In thisexposure, light, which has been passed through the mask 812 and appliedto the photosensitive conductive paste coating 84 exposes thephotosensitive conductive paste coating 84 and, at the same time, istransmitted through the photosensitive conductive paste coating 84 andapplied also to the photosensitive black conductive paste 83. As shownin the drawing, however, the mask 812 has an opening which overlaps withthe opening of the mask 811, avoiding unnecessary exposure of thephotosensitive black conductive paste coating 83. Light sources usableherein are the same as those described above in connection with theprocess for producing an electrode according to the first invention.

Subsequently, the photosensitive black conductive paste coating 83 andthe photosensitive conductive paste coating 84 are developed at a timeand then fired to remove the resin component in photosensitive paste,thereby forming an electrode 85 having a two layer structure of a blackconductive layer 86 and a main conductive layer 87 on the transparentelectrode 82 (FIG. 9C).

FIG. 10 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the thirdinvention. In FIG. 10, a photosensitive black conductive pastecontaining a black pigment is coated so as to cover a transparentelectrode 82 provided on an insulating substrate 81, and the coating isdried to form a photosensitive black conductive paste coating 83, thephotosensitive black conductive paste coating 83 is exposed through amask 811 having a predetermined pattern (FIG. 10A). The photosensitiveblack conductive paste, the process for producing the photosensitiveblack conductive paste coating 83, and the thickness of thephotosensitive black conductive paste coating 83 used herein are thesame as those in the process for producing an electrode according to thefirst invention. Light sources usable herein are the same as thosedescribed above in connection with the process for producing anelectrode according to the first invention.

The exposed photosensitive black conductive paste coating 83 isdeveloped to form a pattern of a black conductive layer 86 (FIG. 10B).Thereafter, a photosensitive conductive paste is coated so as to coverthe pattern, and the coating is then dried to form a photosensitiveconductive paste coating 84, and the photosensitive conductive pastecoating 84 is exposed through a mask 812 having a predetermined pattern(FIG. 10C). The photosensitive conductive paste, the process forproducing the photosensitive conductive paste coating 84, and thethickness of the photosensitive conductive paste coating 84 are the sameas those described above in connection with the process for producing anelectrode according to the first invention. Light sources usable hereinare the same as those described above in connection with the process forproducing an electrode according to the first invention.

Subsequently, the photosensitive conductive paste coating 84 isdeveloped to form a pattern of a main conductive layer 87 and then firedto remove the resin component from the pattern of the black conductivelayer 86 and the pattern of the main conductive layer 87 to form anelectrode 85 having a two layer structure of a black conductive layer 86and a main conductive layer 87 on the transparent electrode 82 (FIG.3D).

[D] Production of Composite Electrode Having Two Layer Structure byTransfer

In this aspect of the present invention, there is provided a transfersheet and a process for producing an electrode which can produce anelectrode having high display quality even in a high-definition orlarge-area plasma display panel.

The transfer sheet for an electrode of a plasma display panel accordingto the first invention comprises: a transfer support; a photosensitiveconductive paste layer separably provided on the transfer support; and aphotosensitive black conductive paste layer, containing a black pigment,provided on the photosensitive conductive paste layer.

The transfer sheet for an electrode of a plasma display panel accordingto the second invention is such that the transfer support is permeableto light.

The transfer sheet for an electrode of a plasma display panel accordingto the third invention comprises: a transfer support; and aphotosensitive black conductive paste layer, containing a black pigment,separably provided on the transfer support.

The transfer sheet for an electrode of a plasma display panel accordingto the fourth invention is such that the transfer support is permeableto light.

The transfer sheet for an electrode of a plasma display panel accordingto the fifth invention comprises: a transfer support; and aphotosensitive conductive paste layer separably provided on the transfersupport.

The transfer sheet for an electrode of a plasma display panel accordingto the sixth invention is such that the transfer support is permeable tolight.

The process for producing an electrode of a plasma display panelaccording to the first invention comprise the steps of: transferring aphotosensitive black conductive paste layer and a photosensitiveconductive paste layer onto an insulating substrate using the transfersheet for an electrode according to the first or second invention;exposing the photosensitive black conductive paste layer and thephotosensitive conductive paste layer through a mask having apredetermined pattern; developing the exposed photosensitive blackconductive paste layer and the exposed photosensitive conductive pastelayer; and performing firing to form an electrode having a two layerstructure of a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the second invention comprises the steps of: bringing thephotosensitive black conductive paste layer side of the transfer sheetfor an electrode according to the second invention into contact with thesurface of an insulating substrate by pressure; exposing thephotosensitive black conductive paste layer and the photosensitiveconductive paste layer from above the transfer support through a maskhaving a predetermined pattern; separating and removing the transfersupport; and performing development and firing to form an electrodehaving a two layer structure of a black conductive layer and a mainconductive layer.

The process for producing an electrode of a plasma display panelaccording to the third invention comprises the steps of: exposing thephotosensitive black conductive paste layer and the photosensitiveconductive paste layer of the transfer sheet for an electrode accordingto the first or second invention through a mask having a predeterminedpattern; transferring the photosensitive black conductive paste layerand the photosensitive conductive paste layer of the transfer sheet ontoan insulating substrate; and developing and firing the transferredphotosensitive black conductive paste layer and photosensitiveconductive paste layer to form an electrode having a two layer structureof a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the fourth invention comprises the steps of: exposing thephotosensitive black conductive paste layer and the photosensitiveconductive paste layer of the transfer sheet for an electrode accordingto the first or second invention through a mask having a predeterminedpattern; developing the exposed photosensitive black conductive pastelayer and the exposed photosensitive conductive paste layer to form ablack conductive layer pattern and a main conductive layer pattern;transferring the black conductive layer pattern and the main conductivelayer pattern in the transfer sheet onto an insulting substrate; andthen performing firing to form an electrode having a two layer structureof a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the fifth invention comprises the steps of: transferring aphotosensitive black conductive paste layer onto a transparentelectrode, provided on an insulting substrate, using the transfer sheetfor an electrode according to the third or fourth invention;transferring a photosensitive conductive paste layer onto thephotosensitive black conductive paste layer using the transfer sheet foran electrode according to the fifth or sixth invention; exposing thetransferred photosensitive black conductive paste layer andphotosensitive conductive paste layer through a mask having apredetermined pattern; developing the exposed photosensitive blackconductive paste layer and photosensitive conductive paste layer; andperforming firing to form an electrode having a two layer structure of ablack conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the sixth invention comprises the steps of: transferring aphotosensitive black conductive paste layer onto an insulting substrateusing the transfer sheet for an electrode according to the third orfourth invention; bringing the photosensitive conductive paste layerside of the transfer sheet for an electrode according to the sixthinvention into contact with the top surface of the photosensitive blackconductive paste layer by pressure; exposing the photosensitive blackconductive paste layer and the photosensitive conductive paste layerfrom above the transfer support through a mask having a predeterminedpattern; separating and removing the transfer support; and performingdevelopment and then firing to form an electrode having a two layerstructure of a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the seventh invention comprises the steps of: transferringa photosensitive black conductive paste layer onto an insultingsubstrate using the transfer sheet for an electrode according to thethird or fourth invention; exposing the transferred photosensitive blackconductive paste layer through a mask having a predetermined pattern;transferring a photosensitive conductive paste layer onto thephotosensitive black conductive paste layer using the transfer sheet foran electrode according to the fifth or sixth invention; exposing thephotosensitive conductive paste layer through a mask having apredetermined pattern; and performing development and then firing toform an electrode having a two layer structure of a black conductivelayer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the eighth invention comprises the steps of: bringing thephotosensitive black conductive paste layer side of the transfer sheetfor an electrode according to the fourth invention into contact with thesurface of an insulating substrate by pressure; exposing thephotosensitive black conductive paste layer from the top of the transfersupport through a mask having a predetermined pattern; separating andremoving the transfer support; bringing the photosensitive conductivepaste layer side of the transfer sheet for an electrode according to thesixth invention into contact with the photosensitive black conductivepaste layer by pressure; exposing the photosensitive conductive pastelayer from above the transfer support through a mask having apredetermined pattern; separating and removing the transfer support; andperforming development and then firing to form an electrode having a twolayer structure of a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the ninth invention comprises the steps of: transferring aphotosensitive black conductive paste layer onto an insulting substrateusing the transfer sheet for an electrode according to the third orfourth invention; exposing the transferred photosensitive blackconductive paste layer through a mask having a predetermined pattern;developing the exposed photosensitive black conductive paste layer toform a black conductive layer pattern; transferring a photosensitiveconductive paste layer using the transfer sheet for an electrodeaccording to the fifth or sixth invention so as to cover the blackconductive layer; exposing the photosensitive conductive paste layerthrough a mask having a predetermined pattern; developing the exposedphotosensitive conductive paste layer to form a main conductive layerpattern; and then performing firing to form an electrode having a twolayer structure of a black conductive layer and a main conductive layer.

The process for producing an electrode of a plasma display panelaccording to the tenth invention comprises the steps of: bringing thephotosensitive black conductive paste layer side of the transfer sheetfor an electrode according to the fourth invention into contact with thesurface of an insulating substrate by pressure; exposing thephotosensitive black conductive paste layer from above the transfersupport through a mask having a predetermined pattern; separating andremoving the transfer support; developing the photosensitive blackconductive paste layer to form a black conductive layer pattern;bringing the photosensitive conductive paste layer side of the transfersheet for an electrode according to the sixth invention into contactwith the black conductive layer pattern by pressure so as to cover theblack conductive layer; exposing the photosensitive conductive pastelayer from above the transfer support through a mask having apredetermined pattern; separating and removing the transfer support;developing the photosensitive conductive paste layer to form a mainconductive layer pattern; and performing firing to form an electrodehaving a two layer structure of a black conductive layer and a mainconductive layer.

The process for producing an electrode of a plasma display panelaccording to the eleventh invention comprises the steps of: exposing thephotosensitive black conductive paste layer in the transfer sheet for anelectrode according to the third or fourth invention through a maskhaving a predetermined pattern; transferring the photosensitive blackconductive paste layer in the transfer sheet onto an insulatingsubstrate; exposing the photosensitive conductive paste layer in thetransfer sheet for an electrode according to the fifth or sixthinvention through a mask having a predetermined pattern; transferringthe photosensitive conductive paste layer onto the photosensitive blackconductive paste layer; and performing development and firing to form anelectrode having a two layer structure of a black conductive layer and amain conductive layer.

The process for producing an electrode of a plasma display panelaccording to the twelfth invention comprises the steps of: exposing thephotosensitive black conductive paste layer in the transfer sheet for anelectrode according to the third or fourth invention through a maskhaving a predetermined pattern; developing the exposed photosensitiveblack conductive paste layer to form a black conductive layer pattern;transferring the black conductive layer pattern provided on the transfersupport onto an insulating substrate; exposing the photosensitiveconductive paste layer in the transfer sheet for an electrode accordingto the fifth or sixth invention through a mask having a predeterminedpattern; developing the exposed photosensitive conductive paste layer toform a main conductive layer pattern; transferring the main conductivelayer pattern in the transfer sheet onto the black conductive layerpattern; and performing firing to form an electrode having a two layerstructure of a black conductive layer and a main conductive layer.

According to the above present invention, in the electrode having a twolayer structure of a black conductive layer and a main conductive layer,provided on an insulating substrate by transfer, using a photosensitivepaste layer provided on a transfer support, the main conductive layerfunctions to lower the electric resistance of the transparent electrode,while the black conductive layer functions to improve the connection ofthe main conductive layer to the transparent electrode and, at the sametime, to enhance the contrast and color purity of the display panel.

According to the present invention, when the substrate is a glasssubstrate, an address electrode for PDP may be formed. On the otherhand, when the substrate is a substrate with a patterned transparentconductive film, a composite electrode (a bus electrode) for PDP may beformed.

The best mode for carrying out the invention will be described.

Transfer Sheet According to the First Invention

FIG. 11 is a schematic cross-sectional view showing one embodiment ofthe transfer sheet for an electrode of a plasma display panel accordingto the first invention. In FIG. 11, a transfer sheet 91 has a structurecomprising a photosensitive conductive paste layer 93 and aphotosensitive black conductive paste layer 94 laminated in that orderonto a transfer support 92. The photosensitive conductive paste layer 93is separably provided on the transfer support 92. A protective film (notshown) formed of the same material as described above may be provided onthe photosensitive black conductive paste layer 94 in order to preventdamage, inclusion of contaminants, blocking and other unfavorablephenomena.

Examples of the transfer support 92 constituting the transfer sheet 91include resin films, such as films of polyethylene terephthalate,polyethylene naphthalate, polyphenylene sulfide, polystyrene,polypropylene, polyethylene, polysulfone, polyamide, polycarbonate,polyvinyl alcohol, polyimide, cellulose derivatives, such as cellophaneand triacetyl cellulose, and ionomers; thin sheets of metals, such asSUS, Al, and Cu; and composites of the above materials. The thickness ofthe transfer support 92 may be 1 to 400 μm, preferably 4.5 to 200 μm.The transfer sheet may be in sheet, continuous, or any other form.Further, a primer layer for regulating the adhesion and releasabilitybetween the transfer support 92 and the photosensitive conductive pastelayer 93 may be provided on the transfer support 92 in its surface onwhich the photosensitive conductive paste layer 93 is to be formed. Theprimer layer may be formed of a vinyl chloride/vinyl acetate copolymer,a (meth)acrylate resin, an isocyanate curing resin, an epoxy resin, asilicone resin (oil), a fluororesin, a polyethylene wax, a carnauba wax,an acrylmelamine resin or the like. The thickness of the primer layermay be about 0.1 to 10 μm.

The photosensitive conductive paste layer 93 constituting the transfersheet 91 comprises at least a conductive powder and a photosensitiveresin component and may be formed by coating, on the transfer support92, a photosensitive conductive paste optionally containing an inorganicpowder for improving the adhesion to a substrate, on which an electrodeis to be formed, or other purposes and drying the coating. Thephotosensitive conductive paste may be coated by blade coating, rollcoating, bead coating, gravure coating, dip coating, Komma coating, diecoating or the like.

The conductive powder may be at least one member selected from Au, Ag,Cu, Ni, Al, Ag—Pd and other powders. The form of particles constitutingthe conductive powder may be any one such as a spherical, flaky, mass,conical, or rod form. Among them, a spherical conductive powder ispreferred from the viewpoints of good light transmission, freedom fromagglomeration and having good dispersibility, and the average particlediameter is preferably 0.05 to 10 μm. When the average particle diameterof the conductive powder is less than 0.05 μm, the structural viscosity(thixotropy) of the photosensitive conductive paste is unfavorablylarge. On the other hand, when the average particle diameter of theconductive powder exceeds 10 μm, the permeability of the photosensitiveconductive paste layer 93 to light applied in the process for producingan electrode according to the present invention which will be describedlater, adversely affecting the exposure of the photosensitive blackconductive paste layer 94. The above conductive powder may beincorporated in an amount of 45 to 93% by weight into the photosensitiveconductive paste layer 93.

Inorganic powders which may be optionally incorporated into thephotosensitive conductive paste layer 93 include, for example, a glassfrit having a softening temperature of 400 to 650° C. and a coefficientof thermal expansion α₃₀₀ of 60×10⁻⁷ to 100×10⁻⁷/° C. When the softeningtemperature of the glass frit exceeds 650° C., the firing temperatureshould be increased. In this case, for example, when the heat resistanceof the insulting substrate, on which an electrode is to be formed, islow, thermal deformation is unfavorably created in the insulatingsubstrate at the stage of firing. On the other hand, when the softeningtemperature of the glass frit is below 400° C., the glass frit is fusedbefore complete decomposition and volatilization of the resin componentin the photosensitive conductive paste layer 93, unfavorably creatingvoids. When the coefficient of thermal expansion α₃₀₀ is less than60×10⁻⁷/° C. or exceeds 100×10⁻⁷/° C., the difference in coefficient ofthermal expansion between the glass frit and the glass substrate, onwhich an electrode is to be formed, is excessively large, creatingdeformation or the like. The average particle diameter of the glass fritis preferably 0.1 to 5 μm.

The photosensitive resin component constituting the photosensitiveconductive paste layer 93 comprises at least an alkali-developablebinder polymer and a monomer and, if necessary, an initiator and asolvent. These materials may be the same as those described above inconnection with the process for producing an electrode pattern. Thesematerials, upon firing, should be volatilized and decomposed and do notleave any carbide in the pattern.

The thickness of the photosensitive conductive paste layer 93 formed ofthe photosensitive conductive paste may be about 2 to 30 μm.

The photosensitive black conductive paste layer 94 constituting thetransfer sheet 91 may be formed by coating a photosensitive blackconductive paste comprising the above photosensitive paste with a blackpigment incorporated thereinto on the photosensitive conductive pastelayer 93 and drying the coating. Coating methods usable herein includeblade coating, roll coating, die coating, bead coating, gravure coating,dip coating, and Komma coating.

Black pigments usable in the photosensitive black conductive pasteinclude conductive black pigments, such as carbon black and titaniumblack, Co—Cr—Fe, Co—Mn—Fe, Co—Fe—Mn—Al, Co—Ni—Cr—Fe, Co—Ni—Mn—Cr—Fe,Co—Ni—Al—Cr—Fe, and Co—Mn—Al—Cr—Fe—Si. The black pigment has an averageparticle diameter of about 0.01 to 5 μm and may be incorporated in anamount of 0.1 to 50 parts by weight based on 100 parts by weight of theconductive powder contained in the photosensitive conductive paste. Whenthe average particle diameter of the black pigment is less than 0.01 μm,the production of such fine particles is difficult and, in addition, thethixotropy of the photosensitive black conductive paste is excessivelylarge. On the other hand, when the average particle diameter exceeds 5μm, uneven color is likely to occur. When the content of the blackpigment is less than 0.1 part by weight, the coloring is unsatisfactory.On the other hand, a black pigment content exceeding 50 parts by weightunfavorably results in increased resistance and, at the same time,remarkably lowered light transmission to cause unsatisfactory curing inexposed areas of the photosensitive black conductive paste layer 94.

The thickness of the photosensitive black conductive paste layer 94formed of the photosensitive black conductive paste may be about 1 to 15μm.

Transfer Sheet of the Second Invention

The transfer sheet for an electrode of a plasma display panel accordingto the second invention is the same as the transfer sheet 91 accordingto the first invention, except that the transfer support 92 is formed ofa resin film permeable to light, such as a film of polyethyleneterephthalate, polyethylene naphthalate, polyphenylene sulfide,polystyrene, polypropylene, polyethylene, polysulfone, polyamide,polycarbonate, polyvinyl alcohol, polyimide, cellulose derivatives, suchas cellophane or triacetyl cellulose, or an ionomer. Imparting lightpermeability to the transfer support 92 permits the photosensitiveconductive paste layer 93 and the photosensitive black conductive pastelayer 94 to be exposed through the transfer support 92. As with thetransfer sheet according to the first invention, a protective film (notshown) may be provided.

Transfer Sheet According to the Third Invention

FIG. 12 is a schematic cross-sectional view showing one embodiment ofthe transfer sheet for an electrode of a plasma display panel accordingto the third invention. In FIG. 12, a transfer sheet 911 has a structurecomprising a photosensitive black conductive paste layer 914 separablyprovided on a transfer support 912. As with the transfer sheet accordingto the first invention, a protective film (not shown) may be provided.

The transfer support 912 constituting the transfer sheet 911 may be thesame as the transfer support 92 constituting the transfer sheet 91according to the first invention. In order to regulate the adhesion andreleasability between the transfer support 912 and the photosensitiveblack conductive paste layer 914, a primer layer may be provided on thetransfer support 912 in its surface on which the photosensitive blackconductive paste layer 914 is to be formed.

As with the photosensitive black conductive paste layer 94 constitutingthe transfer sheet 91 according to the first invention, thephotosensitive black conductive paste layer 914 constituting thetransfer sheet 911 may be one formed by coating a photosensitive blackconductive paste, comprising a photosensitive conductive paste with ablack pigment incorporated thereinto, on a transfer support 912 anddrying the coating.

Transfer Sheet According to the Fourth Invention

The transfer sheet for an electrode of a plasma display panel accordingto the fourth invention is the same as the transfer sheet 911 accordingto the third invention, except that the transfer support 912 is formedof a resin film permeable to light, such as a film of polyethyleneterephthalate, polyethylene naphthalate, polyphenylene sulfide,polystyrene, polypropylene, polyethylene, polysulfone, polyamide,polycarbonate, polyvinyl alcohol, polyimide, cellulose derivatives, suchas cellophane or triacetyl cellulose, or an ionomer. Imparting lightpermeability to the transfer support 912 permits the photosensitiveblack conductive paste layer 914 to be exposed through the transfersupport 912. As with the transfer sheet according to the firstinvention, a protective film (not shown) may be provided.

Transfer Sheet According to the Fifth Invention

FIG. 13 is a schematic cross-sectional view showing one embodiment ofthe transfer sheet for an electrode of a plasma display panel accordingto the fifth invention. In FIG. 13, a transfer sheet 921 has a structurecomprising a photosensitive conductive paste layer 923 separablyprovided on a transfer support 922. As with the transfer sheet accordingto the first invention, a protective film (not shown) may be provided.

The transfer support 922 constituting the transfer sheet 921 may be thesame as the transfer support 92 constituting the transfer sheet 91according to the first invention. In order to regulate the adhesion andreleasability between the transfer support 922 and the photosensitiveconductive paste layer 923, a primer layer may be provided on thetransfer support 922 in its surface on which the photosensitiveconductive paste layer 923 is to be formed.

As with the transfer support 93 constituting the transfer sheet 91according to the first invention, the photosensitive conductive pastelayer 923 constituting the transfer sheet 921 may be one formed bycoating a photosensitive conductive paste on a transfer support 922 anddrying the coating.

Transfer Sheet According to the Sixth Invention

The transfer sheet for an electrode of a plasma display panel accordingto the sixth invention is the same as the transfer sheet 921 accordingto the fifth invention, except that the transfer support 922 is formedof a resin film permeable to light, such as a film of polyethyleneterephthalate, polyethylene naphthalate, polyphenylene sulfide,polystyrene, polypropylene, polyethylene, polysulfone, polyamide,polycarbonate, polyvinyl alcohol, polyimide, cellulose derivatives, suchas cellophane or triacetyl cellulose, or an ionomer. Imparting lightpermeability to the transfer support 922 permits the photosensitiveconductive paste layer 923 to be exposed through the transfer support922. As with the transfer sheet according to the first invention, aprotective film (not shown) may be provided.

The process for producing an electrode according to the presentinvention will be described.

Here the formation of a bus electrode on a transparent electrodeprovided on a front plate of an AC type PDP will be described by way ofexample. However, it should be noted that the bus electrode may beformed directly on an insulating substrate.

Process for Producing an Electrode According to the First Invention

FIG. 14 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the firstinvention. In FIG. 14, at the outset, a photosensitive conductive pastelayer 93 and a photosensitive black conductive paste layer 94 aretransferred using the transfer sheet 91 for an electrode according tothe first or second invention so as to cover a transparent electrode 952provided on an insulating substrate 951 (FIG. 14A). The formation of thephotosensitive conductive paste layer 93 and the photosensitive blackconductive paste layer 94 by transfer may be performed by bringing thetransfer sheet 91 into contact with the transparent electrode 952provided on the insulating substrate 951 by pressure or by pressureunder heating and separating and removing the transfer support 92. Thetransparent electrode 952 may be formed of a conventional transparentconductive material, such as indium tin oxide (ITO) or tin oxide (SnO₂).

The photosensitive conductive paste layer 93 and the photosensitiveblack conductive paste layer 94 are exposed through a mask M having apredetermined pattern (FIG. 14B). In this exposure, light, which hasbeen passed through the mask M and applied to the photosensitiveconductive paste layer 93, exposes the photosensitive conductive pastelayer 93 and, at the same time, is transmitted through thephotosensitive conductive paste layer 93 and exposes the photosensitiveblack conductive paste layer 94. The above exposure may be performedusing a light source, such as a high-pressure mercury lamp, alow-pressure mercury lamp, a medium-pressure mercury lamp, anultrahigh-pressure mercury lamp, a xenon lamp, a mercury short arc lamp,a metal halide lamp, an X-radiation, or an electron beam. In the aboveexposure, when the photosensitive conductive paste layer 93 has noadhesion to the mask M, the exposure may be performed with the mask M inintimate contact with the photosensitive conductive paste layer 93. Onthe other hand, when the photosensitive conductive paste layer 93 hasadhesion to the mask M, it is preferred to provide a space between themask M and the photosensitive conductive paste layer 93.

Subsequently, the photosensitive conductive paste layer 93 and thephotosensitive black conductive paste layer 94 are developed at a timeand then fired to remove the resin component constituting thephotosensitive conductive paste layer 93 and the photosensitive blackconductive paste layer 94, thereby forming an electrode having a twolayer structure of a black conductive layer 954 and a main conductivelayer 953 on the transparent electrode 955 (FIG. 14C).

Process for Producing an Electrode According to the Second Invention

FIG. 15 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the secondinvention. In FIG. 15, the photosensitive black conductive paste layer94 side of the transfer sheet 91 for an electrode according to thesecond invention is brought into contact with an insulating substrate951 having thereon a transparent electrode 952 by pressure so as tocover the transparent electrode 952, and the photosensitive conductivepaste layer 93 and the photosensitive black conductive paste layer 94are exposed from above the transfer support 92 through a mask M having apredetermined pattern (FIG. 15A). In this exposure, light, which hasbeen passed through the mask M, is transmitted through the transfersupport 92 permeable to light to expose the photosensitive conductivepaste layer 93 and, at the same time, is transmitted through thephotosensitive conductive paste layer 93 to expose the photosensitiveblack conductive paste layer 94. By virtue of the exposure from abovethe transfer support 92, the exposure may be performed independently ofthe adhesion of the photosensitive conductive paste layer 93. Lightsources usable herein are the same as those described above inconnection with the process for producing an electrode according to thefirst invention.

Subsequently, the transfer support 92 is separated and removed totransfer the photosensitive conductive paste layer 93 and thephotosensitive black conductive paste layer 94, and the photosensitiveconductive paste layer 93 and the photosensitive black conductive pastelayer 94 are then developed at a time. Thereafter, firing is performedto remove the resin component constituting the photosensitive conductivepaste layer 93 and the photosensitive black conductive paste layer 94 toform an electrode 955 having a two layer structure of a black conductivelayer 954 and a main conductive layer 953 on the transparent electrode952 (FIG. 15B).

Process for Producing an Electrode According to the Third Invention

FIG. 16 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the thirdinvention. In FIG. 16, at the outset, the photosensitive conductivepaste layer 93 and the photosensitive black conductive paste layer 94 inthe transfer sheet 91 for an electrode according to the first or secondinvention are exposed through a mask M having a predetermined pattern(FIG. 16A). In this exposure, light, which has been passed through themask M, exposes the photosensitive black conductive paste layer 94 and,at the same time, is transmitted through the photosensitive blackconductive paste layer 94 to expose the photosensitive conductive pastelayer 93. Preferred light sources for such exposure include ahigh-pressure mercury lamp, a low-pressure mercury lamp, amedium-pressure mercury lamp, an ultrahigh-pressure mercury lamp, axenon lamp, a mercury short arc lamp, a metal halide lamp, anX-radiation, or an electron beam. In the above exposure, when thephotosensitive black conductive paste layer 94 has no adhesion to themask M, exposure may be performed in such a manner that, after theprotective film, if any, is separated and removed, exposure is performedwith the mask M in intimate contact with the photosensitive blackconductive paste layer 94. On the other hand, when the photosensitiveconductive paste layer 94 has adhesion to the mask M, exposure may beperformed with a space provided between the mask M and thephotosensitive black conductive paste layer 94 or alternatively with aprotective film permeable to light provided. When the transfer sheet 91according to the second invention wherein the transfer support 92 ispermeable to light is used, exposure may be performed from the transfersupport 92 side through the mask M. Light sources usable herein are thesame as those described above in connection with the process forproducing an electrode according to the first invention.

The exposed photosensitive conductive paste layer 93 and photosensitiveblack conductive paste layer 94 are transferred so as to cover atransparent electrode 952 provided on an insulating substrate 951 (FIG.16B). Thereafter, the photosensitive conductive paste layer 93 and thephotosensitive black conductive paste layer 94 are developed at a timeand then fired to remove the resin component constituting thephotosensitive conductive paste layer 93 and the photosensitive blackconductive paste layer 94, thereby forming an electrode 955 having a twolayer structure of a black conductive layer 954 and a main conductivelayer 953 on the transparent electrode 952 (FIG. 16C).

Process for Producing an Electrode According to the Fourth Invention

FIG. 17 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the fourthinvention. In FIG. 17, at the outset, the photosensitive conductivepaste layer 93 and the photosensitive black conductive paste layer 94 inthe transfer sheet 91 for an electrode according to the first or secondinvention are exposed through a mask M having a predetermined pattern(FIG. 17A). This exposure may be performed in the same manner as in thethird invention.

The photosensitive conductive paste layer 93 and the photosensitiveblack conductive paste layer 94 are developed at a time to form a mainconductive layer pattern 93′ and a black conductive layer pattern 94′ onthe transfer support 92 (FIG. 17B).

The main conductive layer pattern 93′ and the black conductive layerpattern 94′ are transferred onto a transparent electrode 952, in itspredetermined position, provided on an insulating substrate 51 and thenfired to remove the resin component constituting the main conductivelayer pattern 93′ and the black conductive layer pattern 94′, therebyforming an electrode 955 having a two layer structure of a blackconductive layer 954 and a main conductive layer 953 (FIG. 17C).

Process for Producing an Electrode According to the Fifth Invention

FIG. 18 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the fifthinvention. In FIG. 18, at the outset, a photosensitive black conductivepaste layer 914 is transferred using the transfer sheet 911 for anelectrode according to the third or fourth invention so as to cover atransparent electrode 952 provided on an insulating substrate 951 (FIG.18A). A photosensitive conductive paste layer 923 is transferred usingthe transfer sheet 921 for an electrode according to the fifth or sixthinvention onto the photosensitive black conductive paste layer 914 (FIG.18B).

The photosensitive conductive paste layer 923 and the photosensitiveblack conductive paste layer 914 are exposed through a mask M having apredetermined pattern (FIG. 18C). In this exposure, light, which hasbeen passed through the mask M and applied to the photosensitiveconductive paste layer 923, exposes the photosensitive conductive pastelayer 923 and, at the same time, is transmitted through thephotosensitive conductive paste layer 923 to expose the photosensitiveblack conductive paste layer 914. In the above exposure, when thephotosensitive conductive paste layer 923 has no adhesion to the mask M,the exposure may be performed with the mask M in intimate contact withthe photosensitive conductive paste layer 923. On the other hand, whenthe photosensitive conductive paste layer 923 has adhesion to the maskM, it is preferred to provide a space between the mask M and thephotosensitive conductive paste layer 923. Light sources usable hereinare the same as those described above in connection with the process forproducing an electrode according to the first invention.

The photosensitive conductive paste layer 923 and the photosensitiveblack conductive paste layer 914 are developed at a time and then firedto remove the resin component constituting the photosensitive conductivepaste layer 923 and the photosensitive black conductive paste layer 914,thereby forming an electrode 955 having a two layer structure of a blackconductive layer 954 and a main conductive layer 953 on the transparentelectrode 952 (FIG. 18D).

Process for Producing an Electrode According to the Sixth Invention

FIG. 19 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the sixthinvention. In FIG. 19, at the outset, a photosensitive black conductivepaste layer 914 is transferred using the transfer sheet 911 for anelectrode according to the third or fourth invention so as to cover atransparent electrode 952 provided on an insulating substrate 951 (FIG.19A). The photosensitive conductive paste layer 923 side of the transfersheet 921 for an electrode according to the sixth invention is broughtinto contact with the top surface of the photosensitive black conductivepaste layer 914 by pressure, and the photosensitive conductive pastelayer 923 and the photosensitive black conductive paste layer 914 areexposed from above the transfer support 922 through a mask M having apredetermined pattern (FIG. 19B). In this exposure, light, which hasbeen passed through the mask M, is transmitted through the transfersupport 922 permeable to light to expose the photosensitive conductivepaste layer 923 and, at the same time, is transmitted through thephotosensitive conductive paste layer 923 to expose the photosensitiveblack conductive paste layer 914. By virtue of the exposure from abovethe transfer support 922, the exposure may be performed independently ofthe adhesion of the photosensitive conductive paste layer 923. Lightsources usable herein are the same as those described above inconnection with the process for producing an electrode according to thefirst invention.

Subsequently, the transfer support 922 is separated and removed totransfer the photosensitive conductive layer 923. The photosensitiveconductive paste layer 923 and the photosensitive black conductive pastelayer 914 are developed at a time and then fired to remove the resincomponent constituting the photosensitive conductive paste layer 923 andthe photosensitive black conductive paste layer 914, thereby forming anelectrode 955 having a two layer structure of a black conductive layer954 and a main conductive layer 953 on the transparent electrode 952(FIG. 19D).

Process for Producing an Electrode According to the Seventh Invention

FIG. 20 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to theseventh invention. In FIG. 20, at the outset, a photosensitive blackconductive paste layer 914 is transferred using the transfer sheet 911for an electrode according to the third or fourth invention so as tocover a transparent electrode 952 provided on an insulating substrate951, and the photosensitive black conductive paste layer 914 is exposedthrough a mask M having a predetermined pattern (FIG. 20A).

The photosensitive conductive paste layer 923 in the transfer sheet 921for an electrode according to the fifth or sixth invention istransferred onto the photosensitive black conductive paste layer 914,and the photosensitive conductive paste layer 923 is exposed through amask M′ having a predetermined pattern (FIG. 20B). In this exposure,light, which has been passed through the mask M′, exposes thephotosensitive conductive paste layer 923 and, at the same time, istransmitted through the photosensitive conductive paste layer 923 andapplied to the photosensitive black conductive paste layer 914. As shownin the drawing, the mask M′ has an opening which overlaps with theopening of the mask M, avoiding unnecessary exposure of thephotosensitive black conductive paste layer 914. In such exposure, whenthe photosensitive black conductive paste layer 914 has no adhesion tothe mask M and the photosensitive conductive paste layer 923 has noadhesion to the mask M′, the exposure may be performed with the masks M,M′ in intimate contact respectively with the photosensitive blackconductive paste layer 914 and the photosensitive conductive paste layer923. On the other hand, when the photosensitive black conductive pastelayer 914 and the photosensitive conductive paste layer 923 have anadhesive property, it is preferred to provide a space between the maskand the paste layer. Light sources usable herein are the same as thosedescribed above in connection with the process for producing anelectrode according to the first invention.

Subsequently, the photosensitive conductive paste layer 923 and thephotosensitive black conductive paste layer 914 are developed at a timeand then fired to remove the resin component constituting thephotosensitive conductive paste layer 923 and the photosensitive blackconductive paste layer 914, thereby forming an electrode 955 having atwo layer structure of a black conductive layer 954 and a mainconductive layer 953 on the transparent electrode 952 (FIG. 20C).

Process for Producing an Electrode According to the Eighth Invention

FIG. 21 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the eighthinvention. In FIG. 21, at the outset, the photosensitive blackconductive paste layer 914 side of the transfer sheet 911 for anelectrode according to the fourth invention is brought into contact withan insulating substrate 951 having thereon a transparent electrode 952by pressure so as to cover the transparent electrode 952, and thephotosensitive black conductive paste layer 914 is exposed from abovethe transfer support 912 through a mask M having a predetermined pattern(FIG. 21A). In this exposure, light, which has been passed through themask M, is transmitted through the transfer support 912 permeable tolight to expose the photosensitive black conductive paste layer 914.

The transfer support 912 is then separated and removed, and thephotosensitive conductive paste layer 923 side of the transfer sheet 921for an electrode according to the sixth invention is brought intocontact with the top surface of the photosensitive black conductivepaste layer 914 by pressure, and the photosensitive conductive pastelayer 923 is exposed from above the transfer support 922 through a maskM′ having a predetermined pattern (FIG. 21B). In this exposure, light,which has been passed through the mask M′ and transmitted through thetransfer support 922, exposes the photosensitive conductive paste layer923 and, at the same time, is transmitted through the photosensitiveconductive paste layer 923 to expose the photosensitive black conductivepaste layer 914. In this case, as shown in the drawing, the mask M′ hasan opening which overlaps with the opening of the mask M, avoidingunnecessary exposure of the photosensitive black conductive paste layer914.

By virtue of the exposure from above the transfer support 912 or thetransfer support 922, the exposure may be performed independently of theadhesive property of the photosensitive black conductive paste layer 914and the photosensitive conductive paste layer 923. Light sources usableherein are the same as those described above in connection with theprocess for producing an electrode according to the first invention.

Subsequently, the transfer support 922 is separated and removed, and thephotosensitive conductive paste layer 923 and the photosensitive blackconductive paste layer 914 are developed at a time and then fired toremove the resin component constituting the photosensitive conductivepaste layer 923 and the photosensitive black conductive paste layer 914,thereby forming an electrode 955 having a two layer structure of a blackconductive layer 954 and a main conductive layer 953 on the transparentelectrode 952 (FIG. 21C).

Process for Producing an Electrode According to the Ninth Invention

FIG. 22 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the ninthinvention. In FIG. 22, at the outset, a photosensitive black conductivepaste layer 914 is transferred using the transfer sheet 911 for anelectrode according to the third or fourth invention so as to cover atransparent electrode 952 provided on an insulating substrate 951, andthe photosensitive black conductive paste layer 914 is exposed through amask M having a predetermined pattern (FIG. 22A).

The photosensitive black conductive paste layer 914 is developed to forma black conductive layer pattern 914′ on the transparent electrode 952(FIG. 22B). Thereafter, the photosensitive conductive paste layer 923 inthe transfer sheet 921 for an electrode according to the fifth or sixthinvention is transferred so as to cover the transparent electrode 952and the black conductive layer pattern 914′, and the photosensitiveconductive paste layer 923 is exposed through a mask M′ having apredetermined pattern (FIG. 22C). As shown in the drawing, the mask M′has an opening which overlaps with the opening of the mask M.

The photosensitive conductive paste layer 923 is developed to from amain conductive layer pattern 923′ on the black conductive layer pattern914′ (FIG. 22D).

In the above exposure, when the photosensitive black conductive pastelayer 914 has no adhesion to the mask M and the photosensitiveconductive paste layer 923 has no adhesion to the mask M′, the exposuremay be performed with the masks M, M′ in intimate contact respectivelywith the photosensitive black conductive paste layer 914 and thephotosensitive conductive paste layer 923. On the other hand, when thephotosensitive black conductive paste layer 914 and the photosensitiveconductive paste layer 923 have an adhesive property, it is preferred toprovide a space between the mask and the paste layer. Light sourcesusable herein are the same as those described above in connection withthe process for producing an electrode according to the first invention.

Firing is then performed to remove the resin component constituting themain conductive layer pattern 923′ and the black conductive layerpattern 914′, thereby forming an electrode 955 having a two layerstructure of a black conductive layer 954 and a main conductive layer953 on the transparent electrode 952 (FIG. 22E).

Process for Producing an Electrode According to the Tenth Invention

FIG. 23 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to the tenthinvention. In FIG. 23, at the outset, the photosensitive blackconductive paste layer 914 side of the transfer sheet 911 for anelectrode according to the fourth invention is brought into contact withan insulating substrate 951 having thereon a transparent electrode 952by pressure so as to cover the transparent electrode 952, and thephotosensitive black conductive paste layer 914 is exposed from abovethe transfer support 912 through a mask M having a predetermined pattern(FIG. 23A). In this exposure, light, which has been passed through themask M, is transmitted through the transfer support 912 permeable tolight to expose the photosensitive black conductive paste layer 914.

The transfer support 912 is separated and removed, and thephotosensitive black conductive paste layer 914 is developed to form ablack conductive layer pattern 914′ on the transparent electrode 952(FIG. 23B).

The photosensitive conductive paste layer 923 side of the transfer sheet921 for an electrode according to the sixth invention is pressed so asto cover the transparent electrode 952 and the black conductive layerpattern 914′, and the photosensitive conductive paste layer 923 isexposed from above the transfer support 922 through a mask M′ having apredetermined pattern (FIG. 23C). As shown in the drawing, the mask M′has an opening which overlaps with the opening of the mask M.

By virtue of the exposure from above the transfer support 912 or thetransfer support 922, the exposure may be performed independently of theadhesive property of the photosensitive black conductive paste layer 914and the photosensitive conductive paste layer 923. Light sources usableherein are the same as those described above in connection with theprocess for producing an electrode according to the first invention.

Subsequently, the transfer support 922 is separated and removed, and thephotosensitive conductive paste layer 923 is developed to form a mainconductive layer pattern 923′ on the black conductive layer pattern 914′(FIG. 23D).

Firing is then performed to remove the resin component constituting themain conductive layer pattern 923′ and the black conductive layerpattern 914′, thereby forming an electrode 955 having a two layerstructure of a black conductive layer 954 and a main conductive layer953 on the transparent electrode 952 (FIG. 23E).

Process for Producing an Electrode According the Eleventh Invention

FIG. 24 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to theeleventh invention. In FIG. 24, at the outset, the photosensitive blackconductive paste layer 914 in the transfer sheet 911 for an electrodeaccording to the third or fourth invention is exposed through a mask Mhaving a predetermined pattern (FIG. 24A). In this exposure, when thephotosensitive black conductive paste layer 914 has no adhesion to themask M, the exposure may be performed with the mask M in intimatecontact with the photosensitive conductive paste layer 914. On the otherhand, when the photosensitive black conductive paste layer 914 hasadhesion to the mask M, the exposure is preferably performed in such astate that a space is provided between the mask M and the photosensitiveblack conductive paste layer 914, or alternatively a protective filmpermeable to light may be provided. When the transfer sheet 911according to the fourth invention wherein the transfer support 912 ispermeable to light is used, exposure may be performed from the transfersupport 912 side through the mask M. Light sources usable herein are thesame as those described above in connection with the process forproducing an electrode according to the first invention.

The exposed photosensitive black conductive paste layer 914 is thentransferred so as to cover a transparent electrode 952 provided on aninsulating substrate 951 (FIG. 24B).

Separately, the photosensitive conductive paste layer 923 in thetransfer sheet 921 for an electrode according to the fifth or sixthinvention is exposed through a mask M′ having a predetermined pattern(FIG. 24C). In this exposure, when the photosensitive conductive pastelayer 923 has no adhesion to the mask M′, the exposure may be performedwith the mask M′ in intimate contact with the photosensitive conductivepaste layer 923. On the other hand, when the photosensitive conductivepaste layer 923 has adhesion to the mask M′, the exposure is preferablyperformed in such a state that a space is provided between the mask M′and the photosensitive conductive paste layer 923, or alternatively aprotective film permeable to light may be provided. When the transfersheet 921 according to the sixth invention wherein the transfer support922 is permeable to light is used, exposure may be performed from thetransfer support 922 side through the mask M′. Light sources usableherein are the same as those described above in connection with theprocess for producing an electrode according to the first invention.

The exposed photosensitive conductive paste layer 923 is thentransferred onto the photosensitive black conductive paste layer 914(FIG. 24D).

The photosensitive conductive paste layer 923 and the photosensitiveblack conductive paste layer 914 are developed at a time and then firedto remove the resin component constituting the photosensitive conductivepaste layer 923 and the photosensitive black conductive paste layer 914,thereby forming an electrode having a two layer structure of a blackconductive layer 954 and a main conductive layer 953 on the transparentelectrode 952 (FIG. 24E).

Process for Producing an Electrode According the Twelfth Invention

FIG. 25 is a process diagram showing one embodiment of the process forproducing an electrode of a plasma display panel according to thetwelfth invention. In FIG. 25, at the outset, the photosensitive blackconductive paste layer 914 in the transfer sheet 911 for an electrodeaccording to the third or fourth invention is exposed through a mask Mhaving a predetermined pattern (FIG. 25A). This exposure may beperformed in the same manner as described above in connection with theprocess for producing an electrode according to the eleventh invention.

The photosensitive black conductive paste layer 914 is then developed toform a black conductive layer pattern 914′ on the transfer support 912(FIG. 25B). The black conductive layer pattern 914′ is transferred ontoa transparent electrode 952, in its predetermined position, on aninsulating substrate 951 (FIG. 25C).

Separately, the photosensitive conductive paste layer 923 in thetransfer sheet 921 for an electrode according to the fifth or sixthinvention is exposed through a mask M′ having a predetermined pattern(FIG. 25D). This exposure may be performed in the same manner asdescribed above in connection with the process for producing anelectrode according to the eleventh invention.

The photosensitive conductive paste layer 923 is then developed to forma main conductive layer pattern 923′ on the transfer support 922, andthe main conductive layer pattern 923′ is transferred onto the blackconductive layer pattern 914′ (FIG. 25E).

Subsequently, firing is performed to remove the resin componentconstituting the main conductive layer pattern 923′ and the blackconductive layer pattern 914′, thereby forming an electrode 955 having atwo layer structure of a black conductive layer 954 and a mainconductive layer 953 on the transparent electrode 952 (FIG. 25F).

In the above-described electrode production processes, after thephotosensitive conductive paste layer and the photosensitive blackconductive paste layer are exposed, they may be developed with anaqueous sodium carbonate solution, an aqueous sodium hydroxide solution,an aqueous potassium hydroxide solution, an aqueous potassium carbonatesolution, an organic alkali, such as monoethanolamine, or the like.

EXAMPLES Example A1

As shown in FIG. 2A, a transparent electrode as a sustaining electrode 4was formed on a glass 1 to serve as a front plate. Specifically, a firstlayer was formed using a transparent conductive film having apredetermined shape. The thickness of the transparent conductive filmwas about 0.05 to 0.4 μm. More specifically, SnO₂ was adhered onto aglass substrate to form a transparent conductive film, a resist layerwas formed on an SnO₂ film using a liquid resist (“OMR85,” manufacturedby Tokyo Ohka Kogyo Co., Ltd., Japan) or a dry film resist (“OrdylBF-205,” manufactured by Tokyo Ohka Kogyo Co., Ltd.), and the resistlayer was subjected to pattern exposure or development to form a resistpattern for a transparent electrode, followed by sandblasting to removeunnecessary areas of the SnO₂ film. In the sandblasting, alumina wasused as an abrasive. The resist pattern was then separated to form atransparent electrode having a desired pattern.

Use of the transparent electrode alone results in high resistance value,rendering the transparent electrode unsuitable as the electrode.Therefore, in order to lower the resistance value, a metallic electrodeis formed using a conductive material on the transparent electrode.Conductive materials usable herein include a conductive paste containingany metallic powder of Ag, Au, Ni, or Al or a sheet prepared from theconductive paste. In this example, a conductive paste 21 composed mainlyof Ag (“D590,” manufactured by ESL) was used as the conductive material,and, as shown in FIG. 2B, is subjected to pattern coating in a metallicelectrode form by screen printing. In the drawing, numeral 22 designatesa screen plate, and numeral 23 a squeegee. Subsequently, the coating wasdried at 170° C. and fired at 580° C. to form a metallic electrode as abus electrode 5 as shown in FIG. 2C.

After the metallic electrode was formed in this way on the transparentelectrode, a dielectric paste (“PLS-3232,” manufactured by NipponElectric Glass Co., Ltd.) was laminated to a thickness of 10 to 30 μm byscreen printing or the like, and the laminate was fired to form adielectric layer 7 as shown in FIG. 2D. The formation of the dielectriclayer 7 permitted irregularities in the glass surface, which had beenmatted in a ground glass form by the sandblasting, to be filled with thedielectric layer, resulting in a 10% or more improvement intransmittance over that for the as sandblasted glass substrate.

In the above example, the transparent electrode was formed bysandblasting an SnO₂ film. ITO may be used as the transparent conductivefilm. Further, the transparent electrode may be formed by etching orlift off besides sandblasting.

Further, in the above example, a metallic electrode was formed after theformation of a transparent electrode on the glass substrate.Alternatively, a metallic electrode may be formed by screen printingfollowed by sandblasting to form a transparent electrode.

Example A2

At the outset, as shown in FIG. 3A, a transparent conductive film 31 anda metallic film 32 are formed on a glass substrate 1 to serve as a frontplate.

Specifically, SnO₂ is adhered by spraying onto the glass substrate 1,and a conductive paste composed mainly of Ag (“D590,” manufactured byESL) was coated on the whole area by screen printing or the like. Thecoating was dried at 170° C. and then fired at 580° C. A resist layerwas formed on the metal film 32 using a liquid resist (“OFPR800,”manufactured by Tokyo Ohka Kogyo Co., Ltd. Japan) or a dry film resist(“Ordyl α-530,” manufactured by Tokyo Ohka Kogyo Co., Ltd), and theresist layer was subjected to pattern exposure or development to form aresist pattern 33, as shown in FIG. 3B, which is the same pattern as abus electrode 5. Subsequently, etching was performed with an aqueousFe(NO₃)₃ solution or an aqueous HNO₃ solution (the concentration foreach aqueous solution being 20 to 50% by weight), and the resist pattern33 was separated and removed to form a metallic electrode as a buselectrode 5, as shown in FIG. 3C.

Thereafter, a dry film resist (“Ordyl BF-205,” manufactured by TokyoOhka Kogyo Co., Ltd.) was used to again form a resist layer, followed bypattern exposure and development to form a resist pattern 34, as shownin FIG. 3D, which is the same pattern as a transparent electrode,followed by sandblasting to remove unnecessary areas of the transparentconductive film 31. In the sandblasting, alumina was used as anabrasive. Since the metallic electrode is covered with the resistance,it is not ground by the sandblasting. The resist pattern 34 is separatedand removed to form a transparent electrode as a sustaining electrode 4(FIG. 3E).

After a composite electrode 6 was formed in this way, a dielectric paste(“PLS-3232,” manufactured by Nippon Electric Glass Co., Ltd.) waslaminated to a thickness of 10 to 30 μm by screen printing or the like,followed by firing to form a dielectric layer 7 as shown in FIG. 3F. Theformation of the dielectric layer 7 permitted irregularities in theglass surface, which had been matted in a ground glass form by thesandblasting, to be filled with the dielectric layer, resulting in a 10%or more improvement in transmittance over that for the as sandblastedglass substrate.

Example A3

At the outset, as shown in FIG. 4A, a transparent electrode as asustaining electrode 4 is formed on a glass substrate 1 to serve as afront plate. It is formed in the same manner as in Example A1. Use ofthe transparent electrode alone results in high resistance value,rendering the transparent electrode unsuitable as the electrode.Therefore, in order to lower the resistance value, a metallic electrodeis formed on the transparent electrode. In this example, the metallicelectrode was formed as follows.

A resist layer was formed on a transparent electrode using a liquidresist (“OFPR800,” manufactured by Tokyo Ohka Kogyo Co., Ltd.) or a dryfilm resist (“Ordyl α-530,” manufactured by Tokyo Ohka Kogyo Co., Ltd.),and the resist layer was subjected to pattern exposure and developmentto form a resist pattern 41 having a recess 41 a corresponding to a buselectrode as shown in FIG. 4B. Subsequently, as shown in FIG. 4C, therecess 41 a was filled with a conductive paste 42 (“D590”, manufacturedby ELS) composed mainly of Ag, and the paste 42 was dried at 150° C. Theresist pattern 41 was separated and removed, and the conductive paste 42was fired to form a metallic electrode as a bus electrode 5, as shown inFIG. 4D.

After a metallic electrode was formed in this way on the transparentelectrode, a dielectric paste (“PLS-3232,” manufactured by NipponElectric Glass Co., Ltd.) was laminated by screen printing or the liketo a thickness of 10 to 30 μm and fired to form a dielectric layer 7 asshown in FIG. 4E. The formation of the dielectric layer 7 permittedirregularities in the glass surface, which had been matted in a groundglass form by the sandblasting, to be filled with the dielectric layer,resulting in a 10% or more improvement in transmittance over that forthe as sandblasted glass substrate.

Example A4

At the outset, as shown in FIG. 5A, SnO₂ was adhered onto a glasssubstrate 1 to serve as a front plate 1 by spraying or the like to forma transparent conductive film 51, a resist layer was formed on thetransparent conductive film 51 using a liquid resist (“OFPR800,”manufactured by Tokyo Ohka Kogyo Co., Ltd.) or a dry film resist (“Ordylα-530,” manufactured by Tokyo Ohka Kogyo Co., Ltd.), and the resistlayer was subjected to pattern exposure and development to form a resistpattern 52 having a recess 52 a corresponding to a bus electrode 5 asshown in the drawing. Thereafter, as shown in FIG. 5B, the recess 52 awas filled with a conductive paste 53 composed mainly of Ag (“D590,”manufactured by ESL), and the dielectric paste 53 was dried at 150° C.Subsequently, the resist pattern 52 was separated and removed, and theconductive paste 53 was fired to form a metallic electrode as a buselectrode 5 as shown in FIG. 5C.

Then, the transparent conductive film 51 was patterned to form atransparent electrode as a sustaining electrode 4, as shown in FIG. 5D.The transparent electrode was formed in the same manner as in ExampleA2. Thus, a composite electrode 6 was formed, and a dielectric paste(“PLS-3232,” manufactured by Nippon Electric Glass Co., Ltd.) waslaminated by screen printing or the like to a thickness of 10 to 30 μm,and the laminate was fired to form a dielectric layer 7 as shown in FIG.5E. The formation of the dielectric layer 7 permitted irregularities inthe glass surface, which had been matted in a ground glass form by thesandblasting, to be filled with the dielectric layer, resulting in a 10%or more improvement in transmittance over that for the as sandblastedglass substrate

Example A5

At the outset, as shown in FIG. 6A, a first layer is formed using atransparent conductive film having a predetermined shape on a glassplate 1 to serve as a front plate. That is, a transparent electrode as asustaining electrode 4 is formed. Possible materials for the transparentconductive film include ITO and SnO₂. When ITO is used, a film may beformed by sputtering or vacuum deposition followed by etching accordingto a conventional method. On the other hand, when SnO₂ is used, it ispossible to use a method which comprises the steps of: first forming amask layer, on a glass substrate 1, having a pattern reverse to thepattern of the sustaining electrode 4; forming a film by CVD orspraying; subsequently separating and removing the mask layer to performpattering. An alternative method usable herein comprises adhering SnO₂by spraying or the like to form a film, forming a mask layer having thesame pattern as the sustaining electrode 4, performing patterning bysandblasting or the like, and separating and removing the mask layer.The thickness of the transparent conductive film is about 0.05 to 0.4μm.

Specifically, a 0.15 μm-thick ITO film was formed as a transparentconductive film by sputtering on a soda lime glass plate, a mask layerwas formed using a photoresist (“OFPR800,” manufactured by Tokyo OhkaKogyo Co., Ltd.) on the ITO film, ITO was etched in an aqueous solutioncomposed of a 1:1:0.08 mixture of water, hydrochloric acid, and nitricacid, the photoresist was separated and removed, and the substrate wasthen washed with water and dried to form a sustaining electrode 4 havinga line width of 188 μm.

Subsequently, a second layer to serve as a bus electrode 5 is formedusing a photosensitive conductive material as follows. At the outset, asshown in FIG. 6B, a film of a photosensitive conductive material 61 isformed on the substrate having thereon the sustaining electrode 4. Inthis stage, the photosensitive conductive material 61 is formed in alarger pattern than a desired final shape, that is, the pattern of thebus electrode 5, and, in a later step, is trimmed. The photosensitiveconductive material 61 may be a paste comprising a photosensitivematerial and a metallic powder and sensitive to irradiation with lightsuch as ultraviolet light. For example, a photopolymerizable pastedescribed in Japanese Patent Laid-Open No. 41985/1975 may be used.Metallic powders contained in conventional photopolymerizable pastesinclude powders of Ag, Au, Pt, and Cu. Among them, an Ag powder is mostpreferred from the viewpoints of cost and heat resistance. When thephotosensitive conductive material 61 is in the form of a paste, it maybe coated on the substrate by screen printing or the like and dried toform a film of the photosensitive conductive material 61.

In the present example, a negative-working photosensitive paste composedof a) an Ag powder, b) an acrylic copolymer having a carboxyl group andan ethylenically unsaturated group on its side chain, and c) aphotoreactive compound, and d) a photopolymerization initiator was usedas a photosensitive conductive material. This paste was coated by screenprinting on the whole surface of the glass substrate with the sustainingelectrode formed thereon and then dried in an oven at 100° C. for 30 minto form a film of the photosensitive conductive material having athickness of 10 μm.

Then, as shown in FIG. 6C, the photosensitive conductive material 61 isexposed through a photomask 62. When the photosensitive conductivematerial 61 is of negative-working type, that is, photocurable, exposuremay be performed in the form of the bus electrode 5. On the other hand,when the photosensitive conductive material 61 is of positive-workingtype, exposure may be performed in a pattern reverse to the pattern ofthe bus electrode 5. In general, the line width of the bus electrode 5is not more than ½ of the line width of the sustaining electrode 4.Subsequently, as shown in FIG. 6D, the film of the photosensitiveconductive material 61 in its unnecessary areas is removed to complete acomposite electrode 6. When the photosensitive conductive material 61 isof negative-working type, unexposed areas are removed, while in the caseof the positive-working type, exposed areas are removed. When the abovepolymerizable paste is used as the photosensitive conductive material61, unnecessary areas are removed with a suitable solvent followed byfiring at least 400° C. to burn off the organic component in the paste,thereby sintering the metallic powder.

Specifically, the photosensitive conductive material film is exposed toUV in a bus electrode pattern having a line width of 64 μm and sprayedwith a 0.2 wt % aqueous sodium carbonate solution to remove unexposedareas, and the substrate was washed with water and dried to pattern thephotosensitive conductive material, thereby creating a bus electrodepattern. Further, firing was performed at 580° C. for 10 min to burn offthe organic component of the photosensitive conductive material and, atthe same time, to sinter the Ag powder to form a bus electrode having afinal thickness of 5 μm and a sheet resistance of 6.0 mΩ. The sheetresistance required of the bus electrode 5 is not more than 20 mΩ forPDP of class 40 in. although it varies depending upon the definition ofthe panel and the bus electrode width. The bus electrode 5 formed inthis example well satisfies this requirement.

Thus, after a composite electrode 6 is formed in this way on a glasssubstrate 1 to serve as a front plate, a dielectric paste is laminatedto 10 to 30 μm by screen printing or the like, followed by firing toform a dielectric layer 7 as shown in FIG. 6E. Thereafter, the othercomponents are formed by the conventional process to prepare PDP. Thus,since both the sustaining electrode 4 and the bus electrode 5 are formedby photolithography, the formation accuracy and the alignment accuracyare better than those in the case of the screen printing. Further, inthe formation of the bus electrode 5, no vacuum film formation process,such as sputtering or vacuum deposition, is used, and no etching isrequired, offering advantages of productivity and production cost overthe film process.

Specifically, a dielectric layer and a protective layer were formed by aconventional method on the substrate having thereon the compositeelectrode 6 to complete a front plate. The front plate was combined witha back plate formed by a conventional method, followed by filling of agas to complete a panel. An actual panel lighting test was performed. Asa result, the drive voltage and the panel brightness were similar tothose attained by the conventional panel with a bus electrode ofCr/Cu/Cr.

Example A6

In Example A5, a photosensitive paste containing an Ag powder was usedas the photosensitive conductive material 61. In this case, the buselectrode 5 was observed after sintering and found to have a silver-graycolor characteristic of silver. For this reason, when an image isdisplayed using the completed panel and observed with the naked eye, theimage is viewed in a somewhat raised state. Specifically, in an AC typePDP shown in FIG. 1, as described above, the bus electrode 5 serves alsoas the black matrix. However, in the case of the silver-gray tone, thebus electrode does not satisfactorily function as the black matrix. Insuch a case, a black pigment is incorporated into the photosensitiveconductive material 61 to deepen the tone of the bus electrode 5. Blackpigments usable herein include carbon black; titanium black; oxides,composite oxides, nitrides, and carbides of transition metals, such asNi, Cr, Mn, Cu, and Fe; and mixtures of the above pigments. Among them,carbon black is best suited as the black pigment from the viewpoints ofconductivity and cost.

In this example, carbon black (“Diacarbon,” manufactured by MitsubishiChemical Corporation) was incorporated into the photosensitive paste inExample A5 by means of a triple roll mill to prepare a photosensitivepaste containing a black pigment, and a composite electrode 6 was formedin the same manner as in Example A5, except that this paste was used.This caused the tone of the bus electrode 5 to be changed from silvergray to dark gray. A panel provided with the electrode prepared in thepresent example was tested for lightening. As a result, it was foundthat the contrast of the displayed image was improved over that preparedin Example A5.

As described above, the electrode for PDP according to the presentinvention comprises a first layer of a transparent conductive film and asecond layer of a conductive material, the conductive material being aconductive paste or a sheet of a conductive paste. By virtue of thisconstitution, it is possible to use means such as (a) screen printing ofa conductive paste, (b) etching of a conductive material, (c) filling ofa conductive paste, and (d) photolithography using a photosensitiveconductive material. This eliminates the need to use any vacuum deviceunlike the conventional method wherein a metallic film is formed byutilizing a thin film forming technique such as sputtering or vapordeposition. Therefore, the time taken for the treatment of the substratecan be shortened to enhance the production efficiency. Further, unlikethe conventional method wherein the substrate is accommodated in avacuum device, there is no limitation on the size of the substrate,permitting the present invention to easily cope with an increase in thesize of the panel.

Further, the incorporation of the black pigment into the conductivematerial permits the electrode to serve as a black matrix, resulting inimproved image contrast of the panel.

Example B1

A photosensitive paste composed of: 20 parts by weight of aphotosensitive resin component composed of 50 parts by weight of abinder polymer, with an acid value of 100 mg KOH/g, composed ofmethacrylate and methacrylic acid, 25 parts by weight ofpolyoxyethylated trimethylolpropane triacrylate, and 5 parts by weightof a photoinitiator (“Irgacure 369,” manufactured by CIBA-GEIGY); 100parts by weight of a silver powder, 5 parts by weight of a glass frithaving a softening point of 550° C.; and 20 parts by weight of3-methoxybutyl acetate was coated on a polyethylene terephthalate film,and the coating was dried and then laminated onto a glass substrate at90° C. The laminate was irradiated with ultraviolet light through apredetermined mask, the film was separated and removed, and developmentwas performed with a 0.2% aqueous sodium carbonate solution, followed bysintering at 600° C. to form an electrode pattern having a thickness of10 μm and a width of 70 μm for use as an address electrode for PDP.

Example B2

A photosensitive paste composed of: 20 parts by weight of aphotosensitive resin component composed of 100 parts by weight of abinder polymer prepared by adding 7% by mole of glycidyl methacrylate toa copolymer of ethyl methacrylate with methacrylic acid to give an acidvalue of 100 mg KOH/g, 60 parts by weight of polyoxyethylatedtrimethylolpropane triacrylate, and 10 parts by weight of aphotoinitiator (“Irgacure 907,” manufactured by CIBA-GEIGY); 100 partsby weight of a silver powder, 5 parts by weight of a glass frit having asoftening point of 48° C.; and 20 parts by weight of propylene glycolmonomethyl ether was coated on a polyethylene terephthalate film, andthe coating was dried. A PE film was laminated thereon and rolled. Theroll was then laminated onto a glass substrate at 90° C. by means of anautomatic cut-off laminator. The polyethylene terephthalate film wasseparated and removed, and ultraviolet light was applied through apredetermined mask. The film was separated and removed, and developmentwas performed with a 0.5% aqueous sodium carbonate solution, followed bysintering at 580° C. to form an electrode pattern having a thickness of10 μm and a width of 70 μm for use as an address electrode for PDP.

As described above, in the method for a thick film pattern formationaccording to the present invention, after the formation of a patternforming layer on a film by coating a photosensitive paste on the film,the pattern forming layer is disposed on a substrate to expose thepattern forming layer, simplifying the process and enabling theformation of a pattern having an even film thickness.

Example C

At the outset, a photosensitive conductive paste having the followingcomposition was prepared.

(Composition of Photosensitive Conductive Paste)

Methyl methacrylate/methacrylic acid copolymer with glycidylmethacrylate added thereto (acid value 100 mg KOH/g) . . . 10 parts byweight

Ethylene oxide-modified trimethylolpropane triacrylate . . . 6 parts byweight

Polymerization initiator (Irgacure 369, manufactured by CIBA-GEIGY) . .. 1 part by weight

Polydimethyl siloxane (TSF451-1000, manufactured by Toshiba SiliconeCo., Ltd.) . . . 0.1 part by weight

Dipropylene glycol monomethyl ether . . . 10 parts by weight

Ag powder . . . 70 parts by weight

Glass frit (softening point 550° C., coefficient of thermal expansion80×10⁷/° C.) . . . 4 parts by weight

5 Parts by weight of titanium black (average particle diameter 1.3 μm)was added to 100 parts by weight of the above photosensitive conductivepaste to prepare a photosensitive black conductive paste.

Thereafter, the photosensitive black conductive paste was coated byscreen printing on a glass plate with a patterned transparent electrode(line width 150 μm) of indium tin oxide (ITO) formed thereon, and thecoating was dried to form a 3 μm-thick photosensitive black conductivepaste coating (corresponding to FIG. 8A). Subsequently, the abovephotosensitive conductive paste was coated by screen printing on thephotosensitive black conductive paste coating to form a coating whichwas then dried to form a 12 μm-thick photosensitive conductive pastecoating. Thereafter, ultraviolet light was applied through a mask havingan opening of line with 50 μm to expose at a time the photosensitiveblack conductive paste coating and the photosensitive conductive pastecoating (corresponding to FIG. 8B).

Development was then performed with an aqueous 0.5% Na₂CO₃ solution,followed by firing at a peak temperature of 570° C. to form an electrodehaving a two layer structure of a black conductive layer and a mainconductive layer (line width 40 μm, thickness 9 μm) on the ITOtransparent electrode (corresponding to FIG. 8C).

A plasma display panel was prepared using the glass substrate with anelectrode, having a two layer structure, formed on an ITO transparentelectrode. As a result, the plasma display panel had high displaycontrast and color purity and excellent display quality.

The above example was carried out by the method for electrode formationaccording to the first invention (embodiment [C]). It is a matter ofcourse that the method for electrode formation according to the secondinvention and the method for electrode formation according to the thirdinvention also can provide a plasma display panel having markedlydecreased electric resistance of the ITO transparent electrode, highdisplay contrast and color purity and excellent display quality.

As is apparent from the foregoing detailed description, according to thepresent invention, a photosensitive black conductive paste containing ablack pigment and a photosensitive conductive paste are used to form anelectrode (a bus electrode) having a two layer structure of a blackconductive layer and a main conductive layer on a transparent electrodein an insulating substrate. The main conductive layer in the electrodehaving a two layer structure decreases the electric resistance of thetransparent electrode, while the black conductive layer permits the mainconductive layer to improve the connection to the transparent electrodeand, at the same time, can enhance the contrast and color purity of thedisplay panel. The above construction of the electrode can realize highdisplay quality even in a high-definition or large-area plasma displaypanel. Further, the present invention can advantageously eliminate theneed to use any photoresist and, hence, simplifies the process and, inaddition, has the effect of offering higher electrode formation accuracythan the printing method.

Example D1

At the outset, a photosensitive conductive paste having the followingcomposition was prepared.

(Composition of Photosensitive Conductive Paste)

Methyl methacrylate/methacrylic acid copolymer with glycidylmethacrylate added thereto (acid value 100 mg KOH/g) . . . 10 parts byweight

Ethylene oxide-modified trimethylolpropane triacrylate . . . 6 parts byweight

Polymerization initiator (Irgacure 369, manufactured by CIBA-GEIGY) 1part by weight

Propylene glycol monomethyl ether . . . 10 parts by weight

Ag powder . . . 70 parts by weight

Glass frit (softening point 550° C., coefficient of thermal expansion80×10⁻⁷/° C.) 4 parts by weight

5 parts by weight of titanium black (average particle diameter 1.3 μm)was added to 100 parts by weight of the above photosensitive conductivepaste to prepare a photosensitive black conductive paste.

Thereafter, the above photosensitive conductive paste was gravure-coatedon a polyethylene terephthalate film (Lumirror T, thickness 25 μm,manufactured by Toray Industries, Inc.) as a transfer support, and thecoating was dried to form a photosensitive conductive paste layer(thickness 12 μm). Subsequently, the above photosensitive blackconductive paste was gravure-coated thereon, and the coating was driedto laminate a photosensitive black conductive paste layer (thickness 8μm) onto the photosensitive conductive paste layer, thereby preparing atransfer sheet (having a structure shown in FIG. 11).

Thereafter, the above transfer sheet was used to transfer thephotosensitive conductive paste layer and the photosensitive blackconductive layer onto a glass substrate with a patterned transparentelectrode (line width 150 μm) of indium tin oxide (ITO) formed thereon(corresponding to FIG. 14A). In this case, the transfer was performed bybringing the transfer sheet into contact with the glass substrate bypressure at 100° C.

Thereafter, ultraviolet light was applied through a mask having anopening of line with 80 μm to expose at a time the photosensitiveconductive paste layer and the photosensitive black conductive layer(corresponding to FIG. 14B).

Development was then performed with an aqueous 0.5% Na₂CO₃ solution,followed by firing at a peak temperature of 570° C. to form an electrodehaving a two layer structure of a black conductive layer and a mainconductive layer (line width 70 μm, thickness 8 μm) on the ITOtransparent electrode (corresponding to FIG. 14C).

A plasma display panel was prepared using the glass substrate with anelectrode, having a two layer structure, formed on an ITO transparentelectrode. As a result, the plasma display panel had high displaycontrast and color purity and excellent display quality.

Example D2

At the outset, the photosensitive black conductive paste prepared inExample 1 was roll-coated on a polyethylene terephthalate film (LumirrorT, thickness 12 μm, manufactured by Toray Industries, Inc.) as atransfer support, and the coating was dried to form a photosensitiveblack conductive paste layer (thickness 10 μm), thereby preparing atransfer sheet A (having a structure shown in FIG. 12).

Separately, the photosensitive conductive paste prepared in Example D1was coated by Komma coating on a polyethylene terephthalate film(Lumirror T, thickness 25 μm, manufactured by Toray Industries, Inc.) asa transfer support by Komma coating, and the coating was dried to form aphotosensitive conductive paste layer (thickness 15 μm), therebypreparing a transfer sheet B (having a structure shown in FIG. 13).

Thereafter, the transfer sheet A in its photosensitive black conductivepaste layer side was brought into contact by pressure with a patternedtransparent electrode (line width 150 μm) of indium tin oxide (ITO)formed thereon, and ultraviolet light was applied through a mask havingan opening of line with 50 μm to expose the photosensitive blackconductive paste layer (corresponding to FIG. 21A). Thereafter, thetransfer support was separated and removed, thus transferring thephotosensitive black conductive paste layer.

The transfer sheet B in its photosensitive conductive paste layer sidewas then brought into contact by pressure with the surface of thephotosensitive black conductive paste layer, and ultraviolet light wasapplied through a mask having an opening of line width 50 μm to exposethe photosensitive conductive paste layer (corresponding to FIG. 21B).Thereafter, the transfer support was separated and removed, thustransferring the photosensitive conductive paste layer. In this case,the mask used had an opening which overlaps with the opening of the maskused in the exposure of the photosensitive black conductive paste layer.

Development was then performed with an aqueous 0.5% Na₂CO₃ solution,followed by firing at a peak temperature of 570° C. to form an electrodehaving a two layer structure of a black conductive layer and a mainconductive layer (line width 40 μm, thickness 12 μm) on the ITOtransparent electrode (corresponding to FIG. 21C).

A plasma display panel was prepared using the glass substrate with anelectrode, having a two layer structure, formed on an ITO transparentelectrode. As a result, the plasma display panel had high displaycontrast and color purity and excellent display quality.

The above Example D1 used the transfer sheet of the first invention andwas carried out by the method for electrode formation according to thefirst invention, and Example D2 used the transfer sheet of the fourthinvention and the transfer sheet of the sixth invention and was carriedout by the method for electrode formation according to the eighthinvention. However, it is a matter of course that the use of the othertransfer sheets of the present invention and the practice according theother electrode formation methods of the present invention also canprovide a plasma display panel having markedly decreased electricresistance of the ITO transparent electrode, high display contrast andcolor purity and excellent display quality.

As is apparent from the foregoing detailed description, according to thepresent invention, a transfer sheet comprising a transfer support havingthereon a photosensitive black conductive paste layer containing a blackpigment and a photosensitive conductive paste layer, or alternatively acombination of a transfer sheet comprising a transfer support havingthereon a photosensitive black conductive paste layer containing a blackpigment and a transfer sheet comprising a transfer support havingthereon a photosensitive conducive paste layer is used to form anelectrode (a bus electrode) having a two layer structure of a blackconductive layer and a main conductive layer on a transparent electrodein an insulating substrate. The main conductive layer in the electrodehaving a two layer structure decreases the electric resistance of thetransparent electrode, while the black conductive layer permits the mainconductive layer to be connected to the transparent electrode and, atthe same time, can enhance the contrast and color purity of the displaypanel. The above construction of the electrode can realize high displayquality even in a high-definition or large-area plasma display panel.Further, the present invention can advantageously eliminate the need touse any photoresist and, hence, simplifies the process and, in addition,has the effect of offering higher electrode formation accuracy than theprinting method.

What is claimed is:
 1. A process for producing an electrode of a plasmadisplay panel, comprising the steps of: coating a photosensitive blackconductive paste containing a black pigment on a transparent electrodeformed on an insulating substrate and drying the coating to form aphotosensitive black conductive paste coating; coating a photosensitiveconductive paste on the photosensitive black conductive paste coatingand drying the coating to form a photosensitive conductive pastecoating; exposing the photosensitive black conductive paste coating andthe photosensitive conductive paste coating through a mask having apattern; developing the exposed coatings; and then firing the developedcoatings to form an electrode having a two layer structure of a blackconductive layer and a main conductive layer.
 2. A process for producingan electrode of a plasma display panel, comprising the steps of: coatinga photosensitive black conductive paste containing a black pigment on atransparent electrode formed on an insulating substrate and drying thecoating to form a photosensitive black conductive paste coating;exposing the photosensitive black conductive paste coating through amask having a pattern; coating a photosensitive conductive paste on thephotosensitive black conductive paste coating and drying thephotosensitive conductive paste coating; performing exposure through amask having a pattern; and developing and firing the photosensitiveblack conductive paste coating and the photosensitive conductive pastecoating to form an electrode having a two layer structure of a blackconductive layer and a main conductive layer.
 3. A process for producingan electrode of a plasma display panel, comprising the steps of: coatinga photosensitive black conductive paste containing a black pigment on atransparent electrode formed on an insulating substrate and drying thecoating to form a photosensitive black conductive paste coating;exposing the photosensitive black conductive paste coating through amask having a pattern and developing the exposed photosensitive blackconductive paste coating to form a black conductive layer; coating aphotosensitive conductive paste so as to cover the black conductivelayer and drying the thus coated photosensitive conductive pastecoating; and exposing the photosensitive conductive paste coatingthrough a mask having a predetermined pattern and developing the exposedphotosensitive conductive paste coating to form a main conductive layeron the black conductive layer, thereby preparing an electrode having atwo layer structure.